4.75" Single Groove Pulley fits B Section V-Belt 5L with 3/4" Sheave Bushing BK50HCast Iron 4. 75" Single Groove Belt B Section 5L Pulley with 3 4" Sheave Bushing Masterdrive single groove 4. 75" cast iron pulley sheave with 3 4" H bushing for B section belt is a high quality 2 piece pulley that measures 4. 75" outside diameter and is designed to be used with an H style bushing. This bushing inserts into the center of the pulley and slides over the shaft, as you tighten down the bolts on the H bushing it will tighten down on the