BK45-1" Sheave cast iron Solid Pulley With OD: 4.5" inch for V-belt size B Class 5L (BK451) BK45 1"BK Finished Bore Sheaves for (4L or A or 5L or B Belts) BK Sheaves are accurately machined from fine grained cast iron, statically balanced, They are furbished with Standard Keyseats and Hollow Head Setscrews The V-Belts you that can run in this pulley are 4L, or A or 5L, B, V-Belts. The belt series most common for this pulley is the 4L and A section. Keyway not included Outside diameter: 4.5" inch Bore: 1" inch Belt section size: B Class 5L 1 Groove One pulley Hex set screws keyway : 3/16 X 3/32 BK45-1"