Round U Groove Bearings Guide Plastic-coated Bearing POM Pulley Roller Wheel

Match the Inner Diameter (ID) to your axle bolt or shaft diameter, the Outer Diameter (OD) to the space available in your assembly, and the Width to your rail or groove width. The variant label format is ID×OD×Width in millimeters — for example, U6-30-10 means ID 6 mm, OD 30 mm, Width 10 mm. If you are fitting the wheel onto a V-slot extrusion, the OD and groove angle must match the extrusion profile.

POM (polyoxymethylene, also called acetal or Delrin®) is an engineering thermoplastic known for its high stiffness, low friction coefficient, and excellent dimensional stability. In pulley roller wheels, POM provides a self-lubricating rolling surface that reduces wear on both the wheel and the rail, operates quietly, and does not require external grease — making it well-suited for 3D printers, CNC machines, and light conveyor systems.

Many sizes in this range are designed to ride in the V-slot channel of standard 2020, 2040, and similar aluminum extrusion profiles. Verify that the OD and groove width of the wheel match your specific extrusion slot dimensions before ordering. The U groove profile is a round-bottom groove; if your extrusion uses a sharp V-angle, confirm compatibility with your rail supplier's specifications.

Load capacity depends on the bearing size embedded in each wheel variant. Larger OD wheels contain larger bearings with higher radial load ratings. These wheels are suited for light-to-medium duty applications such as 3D printer carriages, small CNC gantries, and cable guide pulleys. For heavy industrial conveyor loads, contact us to confirm the specific bearing specification for your chosen size.

The pre-installed bearings are typically supplied with metal shields or rubber seals and come pre-greased from the factory. The POM outer shell is inherently self-lubricating, so no additional grease is needed on the rolling surface under normal operating conditions. For high-speed or high-temperature environments, contact us to confirm the bearing seal type for your selected variant.

The 5×27×8 (No bearing) variant is a plain POM roller shell without a pre-installed bearing. This is intended for builders who want to press in their own specific bearing — for example, a stainless steel or ceramic bearing for a specialized environment — or who need a lightweight idler without a rolling element. The bore is sized to accept a standard bearing with the matching outer diameter.

The POM shell has good moisture resistance and will not rust or corrode. However, the pre-installed steel bearing may be susceptible to corrosion in prolonged wet or salt-spray environments. For outdoor or high-humidity applications, consider applying a light bearing grease or contact us to confirm whether a stainless-steel bearing variant is available for your required size.

Most CoreXY and Cartesian 3D printer designs use between 4 and 9 idler/guide wheels depending on the axis configuration. A typical two-axis CNC router gantry may use 6–12 wheels. We offer 1, 2, 3, and 5-piece packs so you can order exactly what your BOM requires. For larger batch builds, ordering the 5-piece pack typically offers the best per-unit value.