Dual-Bearing Timing Belt Idler Pulley (4mm Bore, 18.5mm Diameter, 9.5mm Inside Width)

This 4mm Bore Dual-Bearing Timing Belt Idler Pulley is constructed of two 4mm bore bearings and a polycarbonate plastic pulley. You can slip it onto an M4 screw or 4mm shaft to change the tension and trajectory of a single timing belt.

The polycarbonate plastic pulley provides an ultra-smooth surface for either the smooth or toothed side of a timing belt to run with ease. Its flanges, 9.5mm apart, act as guardrails for belt security.

While one bearing is flush with the plastic pulley, the other is nestled inside. This allows for different offsets according to the direction you mount the idler. And if you attach this idler to your project via tightening a screw or otherwise putting an axial load on the bearings, the rotation will remain as smooth as ever due to the bearings’ inner races being coincident with each other.