Hi-Cap® sheaves (narrow V-belts) are manufactured from class 30 gray iron (30000 lb tensile strength) and can have a maximum speed of 6500 fpm. All Martin sheaves are statically balanced. Dynamic balancing should be considered for any sheaves exceeding 5000 lb. Martin Hi-Cap® Wedge Sheave, Type J Arm/Spoke, Bushed Bore, 1-1/8 to 3-3/4 in Bore, 13.2 in OD, 13.1 in Pitch Diameter, 4 Grooves, 3.062 in Face Width, MST® R1 Bushing, For Use With: 5V Cross Section Belts, Cast Iron