FHP sheaves (fractional horsepower) are light duty sheaves that utilize \"H\" bushings or have a finished bore. They 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 fractional horsepower sheaves come in both single or double groove designs and all have precision machined grooves. Martin FHP Sheave, Arm/Spoke Type C, Series: BK Series, MST® Bushed Bore, 1.378 in Bore Dia, 6-3/4 in Outside Dia, 6 in (A/4L)/6.4 in (B/5L), 1 Groove, 7/8 in Face Width, 2 in Hub Dia, 1/2 in Hub Projection, H Bushing, 1-3/8 in Overall Length, For Use With: A or 4L/B or 5L Cross Section Belts, Cast Iron