This rear derailleur roller uses quality aluminium alloy material, anti-rust and resistance, for long time use. The rear derailleur roller is rust-proof and - anodised. These pulleys run on smooth . Easy to use and install with great durability. This bicycle rear derailleur switch rollers ball bearing mounted pulleys work with smooth . Rear derailleur roller has a of lubrication that ensures a smooth function. The rear derailleur roller is a necessary accessory for your bicycle. It can also reduce the resistance, which can improve the efficiency when cycling. The performance of the rear derailleur roller is very good, for chain transport and speed changes are used on the rear derailleur, for mountain bike road bike. Material:Aluminum alloy colour:blue Package Contents: 2 * wheels 4 * Washer Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.