The Tiny-Clutch 1869 Fractional Revolution Pulley Clutch is based off of our SP75B Wrap Spring Clutch. This clutch features a 48 tooth, XL pitch pulley & a 3 lug (Third Revolution) collar. It has a 1/2" | 12.7mm bore, mounts with a set screw & cross hole, & replaces Federal APD Part # 30-4325.