Gates Powergrip Smooth Idler 9mm Belt – 12mm OD – 5mm ID (M-IDLER-S-D12-9-A-P5-H140)

5mm Internal Diameter. 12mm Outer Diameter. (Which gives an equivalent wrapped diameter to a 20 Tooth Pulley) A highly recommended accompaniment to the Gates Powergrip 2GT Belt. Toothed Idlers used appropriately in place of bearings prevent damage to the belts teeth by allowing it to glide freely and gently cups its teeth as it traverses around the curve. Smoothed Idlers are purposely designed, with correct flanges and clearance to ensure a belt retains a constant tension throughout its entire stroke in a way bearings could never match.