INA Pneumatics, Hydraulics & Power Transmission| RS Components

Producten
- Electronics Components, Power & Connectors
- Batteries
  Batteries
  - Automotive Battery Maintenance(7)
  - Battery Chargers & Battery Accessories(614)
  - Non-Rechargeable Batteries(411)
  - Rechargeable Batteries(599)
- Connectors
  Connectors
  - Audio & Video Connectors(1381)
  - Circular Connectors(18047)
  - Connector Tools & Accessories(3852)
  - General Purpose Rectangular Connectors(241)
  - IC Sockets(1065)
  - Magnetic Connectors & Accessories(21)
  - Mains & IEC Connectors & Accessories(3928)
  - Network & Telecom Connectors(2452)
  - PCB Connectors(52206)
  - Power Connectors(11279)
  - RF & Coaxial Connectors(4494)
  - Smart Connectors(20)
  - Terminal Blocks & DIN Rail Terminals(7624)
  - Terminals & Splices(6692)
  - USB, D-sub & Computing Connectors(8170)
- Displays & Optoelectronics
  Displays & Optoelectronics
  - Displays & Industrial Monitors(1851)
  - Fibre Optic Components(205)
  - IR Emitters & Receivers(215)
  - LED Indicators & Accessories(635)
  - LED Lighting System Components(5311)
  - LEDs & LED Accessories(8986)
  - Laser Modules & Components(141)
  - Optocouplers, Photodetectors & Photointerrupters(5864)
- Passive Components
  Passive Components
  - Capacitors(49969)
  - Ferrite Cores(1974)
  - Fixed Resistors(50624)
  - Inductors(14627)
  - Passive Filters(2329)
  - Rotary Encoders(398)
  - Sounder, Buzzer & Microphone Components(713)
  - Surge Protection Components(915)
  - Variable Resistors(8935)
- PCB Prototyping
  PCB Prototyping
  - EMI & RFI Shielding Materials(530)
  - PCB Cleaning(15)
  - PCB Cutting, Punching, Forming & Drilling(111)
  - PCB Etching & Developing(46)
  - PCB Handling(115)
  - PCB Spacers, Pillars & Supports(1144)
  - Printed Circuit Boards - PCB(738)
- Power Supplies & Transformers
  Power Supplies & Transformers
  - DC-AC Power Inverters(175)
  - DC-DC Converters(16489)
  - Portable Generators & Accessories(3)
  - Power Conditioners(37)
  - Power Supplies - PSUs(8184)
  - Power over Ethernet - PoE(34)
  - Renewable Energy(90)
  - Transformers(3486)
  - Uninterruptible Power Supplies - UPS(305)
- Semiconductors
  Semiconductors
  - Amplifiers & Comparators(9134)
  - Audio Processor Circuits(54)
  - Chip Programmers & UV Erasers(115)
  - Clocks, Timing & Frequency Control Circuits(1294)
  - Crystals, Oscillators & Resonators(4900)
  - Data Converters(4943)
  - Discrete Semiconductors(42882)
  - Display Drivers & Controllers(601)
  - Interface ICs(7298)
  - Memory Chips(3444)
  - Power Management ICs(21520)
  - Processors & Microcontrollers(9867)
  - Programmable Logic Circuits(299)
  - Radio Frequency & Microwave Circuits(365)
  - Semiconductor Development Kits(4220)
  - Sensor ICs(2158)
  - Standard Logic(6670)
  - Video Processor Circuits(98)
- Electrical, Automation & Cables
- Automation & Control Gear
  Automation & Control Gear
  - Circuit Protection & Circuit Breakers(5304)
  - Contactors(6280)
  - Control Relays(1207)
  - Electric Motors, Motor Controllers & Peripherals(5586)
  - Fluid Control Systems(1436)
  - Industrial Push Buttons, Pilot Lights & Control Stations(7979)
  - Industrial Switches(4104)
  - Machine Guarding & Safety(3885)
  - PLCs, HMI & Data Acquisition(3041)
  - Panel Meters & Components(4465)
  - Sensors & Transducers(13860)
  - Solenoids(257)
  - Sounders & Beacons(3042)
  - Temperature Control & Process Heating(1491)
  - Timers & Counters(2233)
- Cables & Wires
  Cables & Wires
  - Audio Video Cable(871)
  - Cable Accessories, Ties & Tools(8714)
  - Cable Conduit, Trunking & Routing(2991)
  - Cable Glands, Strain Relief & Grommets(1860)
  - Coaxial Cable(1464)
  - Computer Cable Assemblies(1766)
  - Electrical Power & Industrial Cable(7536)
  - Network & Communication Cable(2376)
  - Ribbon & Flat Cable(1569)
  - Wire & Single Core Cable(4634)
  - Wire to Board Cable Assemblies(910)
- Enclosures, Storage & Material Handling
  Enclosures, Storage & Material Handling
  - 19-Inch Racking(1849)
  - Brackets(52)
  - Cabinet Hardware(606)
  - Door Hardware(1060)
  - Enclosures(7227)
  - Knobs, Equipment Handles & Hand Wheels(732)
  - Ladders & Steps(143)
  - Material Lifting(346)
  - Material Transport - Castors & Wheels(1557)
  - Material Transport - Conveyor Components(334)
  - Material Transport - Drum Transport & Stands(3)
  - Material Transport - Load Restraint(15)
  - Material Transport - Trucks & Trolleys(136)
  - Structural Systems & Handrails(1106)
  - Transit & Equipment Cases(388)
  - Workshop Equipment & Storage(1197)
- Fuses, Sockets & Circuit Breakers
  Fuses, Sockets & Circuit Breakers
  - Circuit Breakers(2319)
  - Consumer Units & Accessories(175)
  - Electrical Installation Accessories(1241)
  - Fuse Holders(1308)
  - Fuse Tools & Testing(16)
  - Fuses(5525)
  - Fuses - PCB(2690)
  - Lightning Protection(27)
- HVAC, Fans & Thermal Management
  HVAC, Fans & Thermal Management
  - Air Conditioning & Climate Control Units(147)
  - Air Filters & Accessories(364)
  - Air Management Accessories(88)
  - Electronics Heating & Cooling(1940)
  - Electronics Humidity & Pressure Control Devices(29)
  - Fan Parts & Accessories(322)
  - Fans(2599)
  - HVAC Ducting(7)
  - HVAC Sensors & Controllers(122)
- Lighting
  Lighting
  - Emergency Lighting & Safety Lighting(129)
  - Fluorescent Lamps & Tubes(421)
  - HID Lamps(83)
  - Halogen Lamps(153)
  - Incandescent Light Bulbs(454)
  - Indicators & Indicator Components(3883)
  - Infrared Lamps(49)
  - LED Lamps(1051)
  - Light Fittings & Luminaires(1239)
  - Lighting Components & Accessories(708)
  - Neon Lamps(71)
  - Smart Lighting(9)
  - Torches & Handlamps(471)
  - UV Lamps(17)
- Relays
  Relays
  - General Purpose Relay Accessories(733)
  - General Purpose Relays(5323)
  - Interface Relay Modules & Accessories(1116)
  - Reed Relays(453)
  - Solid State Relays & Accessories(2012)
- Robots & Robot Parts
  Robots & Robot Parts
  - Robot Construction Kits(17)
  - Robot Parts(19)
  - Robots(47)
- Switches
  Switches
  - DIP & SIP Switches(1110)
  - Detector Switches(129)
  - Foot Switches & Accessories(115)
  - Hall Effect Switches(19)
  - Joystick Switches & Accessories(241)
  - Key Switches & Accessories(250)
  - Keyboard Switches & Accessories(82)
  - Keypads & Accessories(182)
  - Microswitches & Accessories(2131)
  - Modular Switches & Accessories(388)
  - Piezo Switches(159)
  - Push Button Switches & Accessories(5910)
  - Reed Switches & Accessories(455)
  - Rocker Switches & Accessories(1677)
  - Rotary Switches & Accessories(732)
  - Slide Switches & Accessories(586)
  - Switch Development Kits(118)
  - Switch Mounting Accessories(4)
  - Tactile Switches & Accessories(1718)
  - Thumbwheel Switches & Accessories(36)
  - Toggle Switches & Accessories(1955)
  - Touch Switches & Accessories(233)
- Mechanical Products & Tools
- Abrasives & Engineering Materials
  Abrasives & Engineering Materials
  - Aluminium Tubes, Sheets & Angles(158)
  - Brass Tubes, Sheets & Rods(31)
  - Bronze & Gunmetal Tubes & Rods(28)
  - Carbon Fibre & Felt Sheets(8)
  - Ceramic Rods, Sheets & Beads(29)
  - Copper Rods, Sheets & Bars(20)
  - Insulation Materials(100)
  - Machine Sanding & Grinding(828)
  - Manual Sanding & Sharpening(211)
  - Mild Steel Tube, Sheets & Angles(159)
  - Plastic Rods, Sheets & Tubes(614)
  - Polishing & Finishing(145)
  - Rubber Sheets(65)
  - Shim Stock(90)
  - Stainless Steel Tubes, Sheets & Angles(137)
- Adhesives, Sealants & Tapes
  Adhesives, Sealants & Tapes
  - Adhesive, Sealant & Tape Dispensers(90)
  - Adhesives & Glues(347)
  - Hot Melt Glue Guns & Accessories(37)
  - Sealants(134)
  - Tapes(1249)
- Facilities Cleaning & Maintenance
  Facilities Cleaning & Maintenance
  - Brooms, Mops, Buckets & Dust Pans(416)
  - Car Care & Polishes(24)
  - Cleaners, Degreasers & Removers(77)
  - Cleaning Brushes(272)
  - Cleaning Wipes & Cloths(333)
  - Desktop Cleaning Equipment(29)
  - Electronics Cleaners & Protective Coatings(296)
  - Facility Maintenance Equipment(80)
  - Floor Scrubbers & Accessories(7)
  - Greases, Oils & Lubricants(333)
  - Paint & Painting Supplies(214)
  - Traffic Management & Crowd Control(322)
  - Vacuum Cleaners & Carpet Cleaners & Accessories(167)
  - Washroom Equipment & Supplies(231)
  - Waste Removal Bins & Accessories(107)
- Fasteners & Fixings
  Fasteners & Fixings
  - Channel Support Systems(135)
  - Clips(883)
  - Fastener Kits(96)
  - Girder Fixings(101)
  - Hooks & Eyes(16)
  - Levelling & Vibration Control(1426)
  - Magnets & Magnetic Strips(318)
  - Nails(102)
  - Nuts & Washers(579)
  - Pins, Keys & Retaining(151)
  - Rivets & Riveting Tools(160)
  - Screws & Bolts(3052)
  - Sheet Metal & Panel Fasteners(162)
  - Spacers & Standoffs(937)
  - Threaded Rods & Studs(157)
  - Wall Plugs, Anchors, Fixings & Kits(666)
  - Wire Rope Suspension Systems(6)
- Plumbing & Pipeline
  Plumbing & Pipeline
  - Central Heating & Process Pumps(384)
  - Pipe & Tank Insulation(30)
  - Pipe Fittings & Accessories(1450)
  - Pipe Sealants & Cements(5)
  - Pipes, Tubing, and Hoses(1702)
  - Pipework Repair & Maintenance Supplies(82)
  - Radiator Valves & Controllers(16)
  - Sinks & Toilets(22)
  - Solar Thermal & Electric Water Heating(13)
  - Valves & Taps(1837)
  - Water Meters, Thermometers & Pressure Gauges(29)
  - Water Supply Filters(18)
- Pneumatics, Hydraulics & Power Transmission
  Pneumatics, Hydraulics & Power Transmission
  - Electric Actuators(268)
  - Hydraulic & Pneumatic Tools(12)
  - Hydraulic Adaptors, Fittings & Couplings(426)
  - Hydraulic Cylinders, Pumps & Power Units(114)
  - Hydraulic Fluids & Filtration(222)
  - Hydraulic Instrumentation & Switches(151)
  - Hydraulic Tubing & Hose(210)
  - Hydraulic Valves & Manifolds(217)
  - Pneumatic & Hydraulic Pressure Gauges(18)
  - Pneumatic Adaptors, Fittings & Couplings(6568)
  - Pneumatic Air Compressors, Boosters & Vacuum Pumps(282)
  - Pneumatic Air Preparation(3146)
  - Pneumatic Counters, Logic Controllers & Timers(49)
  - Pneumatic Cylinders & Actuators(4698)
  - Pneumatic Instrumentation & Switches(879)
  - Pneumatic Tubing & Air Hose(1016)
  - Pneumatic Valves & Manifolds(4216)
  - Power Transmission - Linear Bearings, Housings & Blocks(364)
  - Power Transmission - Bearing Tools(11)
  - Power Transmission - Belts(1446)
  - Power Transmission - Bushes & Collars(566)
  - Power Transmission - Clutches & Brakes(57)
- Tools
  Tools
  - Air Power Tools(112)
  - Cable & Connector Tools(78)
  - Chalk Lines & Refills(9)
  - Clamps & Vices(313)
  - Corded Power Tools(217)
  - Cordless Power Tools(345)
  - Deburring & Finishing Tools(215)
  - Hammer, Punches & Chisels(491)
  - Knives, Scissors & Multi-tools(528)
  - Machine Tools & Accessories(189)
  - Magnetisers(5)
  - Manual Grease Guns & Accessories(14)
  - Manual Saws & Planers(158)
  - Milling Cutting Tools(245)
  - Mini Power Tools(76)
  - Pliers(1067)
  - Plumbing Tools & Pipe Benders(21)
  - Positioners & Retrieval Tools(605)
  - Power Grinders(66)
  - Power Tool Accessories & Drill Bits(2328)
  - Pullers & Extraction Tools(140)
  - Screwdrivers & Screw Extractors(3392)
  - Shovels & Trowels(61)
  - Soldering & Desoldering Tools(2245)
  - Spanners & Sockets(4798)
  - Threading Tools(878)
  - Tool Kits & Tool Storage(811)
  - Turning & Boring Tools(253)
  - Vehicle & Tyre Tools(23)
  - Welding & Brazing Tools(149)
- IT, Test & Safety Equipment
- Computing & Peripherals
  Computing & Peripherals
  - 3D Printing & Scanning(641)
  - Audio & Video(191)
  - Barcode Readers & Accessories(44)
  - Data Storage & Memory(1680)
  - Embedded Systems(96)
  - KVM, Splitters & Extenders(604)
  - Keyboards & Mice(233)
  - Mobile Computing(90)
  - Networking & Connectivity(777)
  - Optical Drives & Media(22)
  - Photography & Imaging(71)
  - Printers & Printing Supplies(1060)
  - Software(23)
  - Telecommunications(207)
  - Wearable Technology(11)
  - Wireless Components & Modules(1323)
- Office Supplies
  Office Supplies
  - Audio Equipment(26)
  - Books & Training Materials(48)
  - Clocks, Timers & Stopwatches(40)
  - Food & Beverage Preparation(6)
  - Furniture & Desk Accessories(136)
  - Labelling, Binding & Laminating(766)
  - Microphones & Headphones(49)
  - Notice Boards, Wall Planners & Posters(52)
  - Package Strapping, Sealing & Opening(63)
  - Paper Supplies(114)
  - Presentation Tools(15)
  - Speakers & Components(199)
  - Video & Visuals Equipment(25)
  - White Boards & White Board Accessories(43)
  - Writing & Drawing Instruments & Accessories(142)
- Safety, Security, ESD Control & Clean Room
  Safety, Security, ESD Control & Clean Room
  - Floor Mats, Markings & Accessories(222)
  - Impact Protection(22)
  - Keys, Safes, Locks & Lockouts(704)
  - Personal Protection - Welding(73)
  - Personal Protection Clothing & Footwear(4506)
  - Personal Protection Equipment(960)
  - Safety & Security Signs & Accessories(678)
  - Security Alarms, Detectors & Accessories(227)
  - Security Identification Badges & Accessories(11)
  - Spill Clean Up(230)
- Test & Measurement
  Test & Measurement
  - Air & Gas Measurement(235)
  - Bench Power and Power Measurement(1457)
  - Calibrators(174)
  - Data Acquisition & Logging(397)
  - Data Cable & Network Test Equipment(226)
  - Electrical Installation Testing & Accessories(358)
  - Electrical Test Equipment(743)
  - Electronic Component Testing(169)
  - Environmental Measurement(156)
  - Laboratory Equipment(280)
  - Level & Angular Measurement(235)
  - Light & Electromagnetic Radiation Measurement(60)
  - Linear Measurement(810)
  - Liquid Analysis(137)
  - Magnification(361)
  - Multimeters & Accessories(1131)
  - Oscilloscopes & Accessories(1753)
  - Portable Appliance Testers & Accessories(134)
  - Power Measurement(107)
  - Pressure Measurement(1251)
  - RF Test Equipment & Accessories(54)
  - Rotational Measurement(68)
  - Signal Generators & Analysers(347)
  - Sound & Vibration Measurement(73)
  - Temperature Measurement(825)
  - Test Connectors(2491)
  - Test Leads(1055)
  - Weight & Force Measurement(850)
  - Workshop Inspection & Accessories(134)
Merken
- Top merken
- Alle merken
Nieuwe producten
Mijn account
Services

Nieuw € 19,89Each Voorraad checken Vergelijken	Inner Ring 50mm x 60mm x 28mm Inside Diameter50mm Outside Diameter60mm Race Width28mm Bore TypeParallel MaterialSteel Bekijk vergelijkbare producten in categorie Roller Bearings	RS-stocknr. 194-7077 Fabrikant INA Fabrikantnummer IR50X60X28-XL
Nieuw € 16,79Each Voorraad checken Vergelijken	Radial spherical plain bearing 15mm id 2 Bore Size15mm Outside Diameter26mm Static Radial Load Rating44600N Bekijk vergelijkbare producten in categorie Spherical Bearings	RS-stocknr. 191-3872 Fabrikant INA Fabrikantnummer GE15-UK
Nieuw € 17,57Each Voorraad checken Vergelijken	Inner Ring 55mm x 60mm x 25mm Inside Diameter55mm Outside Diameter60mm Race Width25mm Bore TypeParallel MaterialSteel Bekijk vergelijkbare producten in categorie Roller Bearings	RS-stocknr. 194-7078 Fabrikant INA Fabrikantnummer IR55X60X25-XL
Nieuw € 49,84Each Voorraad checken Vergelijken	Radial spherical plain bearing 20mm id 4 Bore Size20mm Outside Diameter42mm Static Radial Load Rating128000N Bekijk vergelijkbare producten in categorie Spherical Bearings	RS-stocknr. 191-3873 Fabrikant INA Fabrikantnummer GE20-FW
€ 36,92Each Voorraad checken Vergelijken	12mm Radial Ball Bearing 47.3mm O.D Inside Diameter12mm Outside Diameter47.3mm Ball Bearing TypeRadial Race Width17.6mm End TypeSealed Bekijk vergelijkbare producten in categorie Ball Bearings	RS-stocknr. 137-1517 Fabrikant INA Fabrikantnummer RABRB12/47FA106
Nieuw € 136,16Each Voorraad checken Vergelijken	Stud type track roller, full complemet n TypeStud Roller Diameter72mm Roller Length80mm Static Load Rating85000N Dynamic Load Rating36500N Bekijk vergelijkbare producten in categorie Track Rollers	RS-stocknr. 194-7218 Fabrikant INA Fabrikantnummer KRV72-PP-A
Nieuw € 25,99Each Voorraad checken Vergelijken	Inner Ring 60mm x 70mm x 28mm Inside Diameter60mm Outside Diameter70mm Race Width28mm Bore TypeParallel MaterialSteel Bekijk vergelijkbare producten in categorie Roller Bearings	RS-stocknr. 194-7087 Fabrikant INA Fabrikantnummer IR60X70X28-XL
€ 59,62Each Voorraad checken Vergelijken	30mm Angular Contact Ball Bearing 55mm O.D Inside Diameter30mm Outside Diameter55mm Ball Bearing TypeAngular Contact Race Width19mm End TypeSealed Bekijk vergelijkbare producten in categorie Ball Bearings	RS-stocknr. 174-0973 Fabrikant INA Fabrikantnummer 30062RS
Nieuw € 16,05Each Voorraad checken Vergelijken	Inner Ring 40mm x 45mm x 30mm Inside Diameter40mm Outside Diameter45mm Race Width30mm Bore TypeParallel MaterialSteel Bekijk vergelijkbare producten in categorie Roller Bearings	RS-stocknr. 194-7055 Fabrikant INA Fabrikantnummer IR40X45X30-XL
€ 26,06Each Voorraad checken Vergelijken	INA Bearing Unit Insert RAE12-XL-NPP-FA106 Inside Diameter12mm Outside Diameter40mm Static Load Rating4750N Dynamic Load Rating10100N Bekijk vergelijkbare producten in categorie Bearing Units - Inserts & Accessories	RS-stocknr. 174-1395 Fabrikant INA Fabrikantnummer RAE12-XL-NPP-FA106
Nieuw € 9,47Each Voorraad checken Vergelijken	Radial spherical plain bearing 6mm id 14 Bore Size6mm Outside Diameter14mm Static Radial Load Rating17000N Bekijk vergelijkbare producten in categorie Spherical Bearings	RS-stocknr. 191-3882 Fabrikant INA Fabrikantnummer GE6-DO
Nieuw € 39,24Each Voorraad checken Vergelijken	Radial spherical plain bearing 20mm id 3 Bore Size20mm Outside Diameter35mm Static Radial Load Rating113000N Bekijk vergelijkbare producten in categorie Spherical Bearings	RS-stocknr. 191-3874 Fabrikant INA Fabrikantnummer GE20-UK-2RS-A
Nieuw € 6,44Each Voorraad checken Vergelijken	Drawn cup needle roller bearing 16mm id Inside Diameter16mm Outside Diameter22mm Roller Bearing TypeDrawn Cup Needle Race Width14mm Bore TypeParallel Bekijk vergelijkbare producten in categorie Roller Bearings	RS-stocknr. 191-3824 Fabrikant INA Fabrikantnummer HK1614-RS-L271
Nieuw € 8,08Each Voorraad checken Vergelijken	Inner Ring 6mm x 10mm x 10mm with lubric Inside Diameter6mm Outside Diameter10mm Race Width10mm Bore TypeParallel MaterialSteel Bekijk vergelijkbare producten in categorie Roller Bearings	RS-stocknr. 194-7088 Fabrikant INA Fabrikantnummer IR6X10X10-IS1-XL
Nieuw € 21,04Each Voorraad checken Vergelijken	Inner Ring 55mm x 60mm x 35mm Inside Diameter55mm Outside Diameter60mm Race Width35mm Bore TypeParallel MaterialSteel Bekijk vergelijkbare producten in categorie Roller Bearings	RS-stocknr. 194-7079 Fabrikant INA Fabrikantnummer IR55X60X35-XL
€ 26,19Each Voorraad checken Vergelijken	INA Bearing Unit Insert RAE15-XL-NPP-FA106 Inside Diameter15mm Outside Diameter40mm Static Load Rating4750N Dynamic Load Rating10100N Bekijk vergelijkbare producten in categorie Bearing Units - Inserts & Accessories	RS-stocknr. 174-1396 Fabrikant INA Fabrikantnummer RAE15-XL-NPP-FA106
€ 272,28Each Voorraad checken Vergelijken	INA Linear Guide Carriage KWSE25-H-G3-V2, KWSE25 Manufacturer SeriesKWSE25 For Rail Width23mm Carriage Length81.8mm Carriage Width70mm Dynamic Load Rating28000N Bekijk vergelijkbare producten in categorie Guide Blocks & Guide Carriages	RS-stocknr. 172-1046 Fabrikant INA Fabrikantnummer KWSE25-H-G3-V2
€ 36,92Each Voorraad checken Vergelijken	15mm Radial Ball Bearing 47.3mm O.D Inside Diameter15mm Outside Diameter47.3mm Ball Bearing TypeRadial Race Width18mm End TypeSealed Bekijk vergelijkbare producten in categorie Ball Bearings	RS-stocknr. 137-1518 Fabrikant INA Fabrikantnummer RABRB15/47FA106
Nieuw € 95,03Each Voorraad checken Vergelijken	Needle Roller Bearing 85mm x 105mm x 23m Inside Diameter85mm Outside Diameter105mm Roller Bearing TypeNeedle Race Width23mm Bore TypeParallel Bekijk vergelijkbare producten in categorie Roller Bearings	RS-stocknr. 191-4424 Fabrikant INA Fabrikantnummer NK85/25-XL
€ 31,05Each Voorraad checken Vergelijken	Roller Clutch Bearing ID35, OD42mm W20mm SeriesHF Inside Diameter35mm Outside Diameter42mm Race Width20mm Torque121Nm Bekijk vergelijkbare producten in categorie Sprag Clutch Bearings	RS-stocknr. 174-1070 Fabrikant INA Fabrikantnummer HF3520-L564

Pneumatics, Hydraulics & Power Transmission

Categorieën