Smooth Idler Pulley Width=11~32mm Timing Belt Idler Drive Pulley Bore=3mm~15mm

Match the belt groove width to the width of your timing belt. For example, if you are using a 15 mm wide GT2 belt, select the 16 mm groove width option. The groove should be slightly wider than the belt to allow free tracking without excessive lateral play.

NEMA 17 stepper motors typically have a 5 mm output shaft. Select the 5 mm bore option. If you plan to mount the idler on a fixed axle bolt rather than a motor shaft, choose a bore that matches your bolt or bearing outer diameter.

Yes. Because these are smooth (toothless) idler pulleys, they are compatible with any flat or round timing belt profile — including GT2, 3GT, 5M, and similar open-end belts — as long as the belt width matches the selected groove width.

The aluminum alloy body provides solid rigidity for typical DIY and light industrial drive applications. For high-speed or high-tension applications, verify that the OD and bore combination you select provides adequate wall thickness between the bore and the groove floor. Larger OD options naturally offer more material and greater load capacity.

Aluminum alloy naturally forms a thin oxide layer that protects against further corrosion in typical indoor environments. For humid or outdoor applications, consider applying a light coating of dry lubricant or anodizing the surface for additional protection.

These are designed as smooth idler pulleys for tensioning and redirecting belts, not for driving them. Because the groove is toothless, the belt can slip under load if used as a drive pulley. For driven applications, use a toothed timing pulley matched to your belt profile.

The bore is a through-hole sized to the selected diameter. You can mount directly on a fixed shaft or press in a standard bearing (such as a 608 or MR series) if you need the pulley to spin freely on a stationary axle. Check the bore dimension against your bearing OD before ordering.