Heavy Duty Garage Door Track Rollers Rolling Gate Sealed Bearing Idler Wheels Specification Diameter(approx.):45.6mm (Detail size as shown in the picture) Material:Plastic and metal Feature 1. and . 2.It is durable and convenient. 3. Simple design and easy to use. 4.These rollers will quiet the door to an unbelievable degree and last longer than the door itself. 5.These rollers use regular motor oil in a dispenser for lubrication.(Lubricate the outside roller wheel and the door track, Roller bearings are sealed and need NO lubrication) Note: 1.We provide clear pictures, measurements where possible. Please check as much as possible to make sure the item is the one that you need. 2.Please allow 0.5-1 inch difference due to manual measurement.(1 inch=2.54cm) 3.The color of the actual items may slightly different from the listing images due to different computer screen, thanks for your understanding. 4.No Instructions Included.Professional Installation Is Highly Recommended Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.