Idler Pulley Wheel for 6mm BeltOD: 18mm ID: 4mm, 5mm or 6mm (624ZZ, 695ZZ, 686ZZ Ball Bearing Built-in) For 6mm wide belt, up to 7.5mm Belt It's works great with our 18T, 20T MXL and GT2 Pulley, Built-in 624ZZ, 695ZZ or 686ZZ Ball Bearing can be mounted onto 4mm, 5mm or 6mm shaft or rod idler or ten...