10 pulleys in one set. Made of iron and plastic, with ball bearings inside, smooth running and durable. Suitable for your wardrobe, bookcase, glass cabinet and other office furniture. The diameter of the wheel is 19 mm, please check the size of your furniture to ensure that the pulley meets your needs before purchasing. This caster is made for the U-shaped rail. Diameter of each caster: 1.9 cm. Width between two casters inner dimension: 2 cm. The casters have a small support to properly position and wedge the door before fixing it. Even doors of 2 and 50 meters high slide well. Although small in size, enough to support about 40 kg.