Brand new single groove 4" pulley for B / 5L belts. This is a high quality cast iron pulley. This pulley is designed to fit a 7/8" keyed shaft and features dual set screws to ensure a completely secure fitting. Most pulleys that are similar to this only have one set screw which makes them less reliable in many working conditions. This pulley is designed to be used with B Belts (also known as 5L Belts). You can use A Belts with this pulley; however, they will sit deeper in the grooves and reduce your pulley size.