10 pulleys in one set. Made of iron and plastic, with ball bearings inside, smooth and durable. Suitable for your wardrobe, bookcase, showcase and other office furniture. The wheel diameter is 19mm. Please check the size of your furniture before purchasing to make sure the roller meets your needs. This roller is suitable for U-shaped rails. Diameter of each roller: 1.9cm. Inner dimension of width between two rollers: 2cm. The rollers have a small support to properly position and wedge the door before fixing. Even doors with a height of 2 and 50 meters slide well. Although small, it is enough to support about 40kg.