USED This two groove sheave measures; 4" for the outer diameter and 3 1/5" for the inner diameters which are measured from the bottoms of the grooves according to standard pulley measurements. The sheave measures 1 1/2" thick excluding the hub. The hub itself measures 3/4" for the inner diameter where the shaft would be located. The groove on the inside of the inner diameter measures 1/8" by 3/16". The original manufacturer and part number are unknown.