Features： 1、Made of CNC aluminum alloy, lightweight and durable 2、Anti rust and corrosion resistant anodized 3、These pulleys run on smooth ball bearings 4、A necessary accessory for your bicycle 5、Apply for most of rear derailleur on the market, support 7/8/9/10 speed Specification： Description: Anodized CNC machined bicycle jockey wheel with fully rubber sealed bearing for center bolt derailleurs. It run on smooth ball bearings, and it's a necessary accessory for your bicycle. There are three different colors for you to choose from, to meet different needs.  Fits for  most of rear derailleur on the market, support 7/8/9/10 speed.  Hope you will enjoy your cycling. Have a nice day. Features: 1. Made of CNC aluminum alloy, lightweight and durable. 2. Anti rust and corrosion resistant anodized. 3. These pulleys run on smooth ball bearings. 4. A necessary accessory for your bicycle. 5. Apply for most of rear derailleur on the market, support 7/8/9/10 speed. Specifications: Material: 7005 Aluminium Alloy Components:  Derailleurs Structure:  Ceramic Bearings Color: Red, Blue, Silver (optional) Size: 11T, 13T (optional) Use: For 7/8/9/10 speed Diameter: 11T-40mm, 13T-50mm Quantity: 2pcs Package Weight: approx. 20g-11T, 23g-13T Fit For: For 4/5/6mm  roller screw axis Package Included: 2 x  Ceramic Bearings Note: 1.  Please allow 1-3mm error due to manual measurement. Thanks for your understanding. 2. Monitors are not calibrated same, item color displayed in photos may be showing  slightly different from the real object. Please in kind prevail. Package List：