Features: brand new and high quality It can restrain the horizontal swing of the chain effectively and make the speed change more accurate. Made of high-strenth aluminum alloy,CNC cutting / anode coloring. Package include:1 x wheel pulley + 2 x reducing sleeves + 1x screw. Two reducing sleeves are presented as a gift, which is more compatible, and can be converted to 4/5MM bearing after installation, which is flexible in rotation. Using ceramic bearings, more smooth and quick response, circlip type design, do not worry about the bearing will rub the edge and cause abnormal noise. Specifications: Material: Aluminum Alloy + Ceramic Color: Black Red Gold Specification: 11T 12T 13T 14T 15T 16T 17T Note: Please allow 0-1cm error due to manual measurement. Make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you Package includes: 1 x Wheel Pulley, 2 x Reducing Sleeve, 1x Screw.