2-A-1 (50-A-1) Solid Sheave Pulley for V-belts 3L, 4LStandard V Pulley 2 A 1 (50 A 1) Solid Sheave Pulley for V belts size 3L, 4L "Shaft hole, keyway and push screw machining standardized." Features Japan's first standard inch size product. Consistent production from casting to machining and surface treatment. Cell production method allows the production of many kinds of products in low volume, with short lead times. Imbalance mass allowance on outer circumference is 0. 2% of pulley mass or 3 g,