VP sheaves (variable pitch) are manufactured from class 30 gray iron (30,000 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 fpm, or if they will be used on equipment where vibration is a problem. Martin variable pitch sheaves have both single and double groove designs and come with a full range of popular bore sizes including keyway and setscrew. They have a positive locking system and precision machined grooves. Martin Variable Pitch Sheave, Bored-to-Size Type A, Finished Bore, 1/2 in Bore Dia, 3.15 in Outside Dia, 1.9 to 2.8 in, 1 Groove, 2-1/4 in Hub Dia, 1-29/32 in Overall Length, For Use With: 3L/A or 4L/B or 5L Cross Section Belts, Class 30 Gray Cast Iron