Specifications Hign-concerned Chemical:None Flywheel Adjustable Gear Number:7-speed Material:Steel Gear Teeth:20 - 26T Freewheel Speed:7 Origin:Mainland China Components:Freewheel 5/6/7 Speed Bicycle Cassette 11-21T/26T/28T Bike Sprocket Bike Cassette Freewheel Compatible with Brompton Folding Bicycle Cassette Flywheel Feature: 1.Upgradable Speed Design: Easily upgrade from 3-speed to a higher number of speeds, the bike cassette freewheel allowing for precise gear control and adapting to different riding scenarios and rider preferences. 2.Hollow Lightweight Construction: Utilizing advanced hollowing techniques, the bicycle freewheel significantly reduces weight, minimizing the burden during rides and enhancing overall riding comfort. 3.High Strength and Durability: Constructed with high-quality metal materials, the bike sprocket ensures stable performance and long-lasting durability even under intense usage conditions. 4.Multiple Spec Options: Provides a variety of bicycle cassette specifications to cater to the individual preferences and requirements of different folding bicycles and riders. 5.Premium Anti-Slip Teeth: The bike freewheel's teeth are specially designed to enhance engagement with the chain, effectively preventing slippage and ensuring safe riding conditions. Specification: Origin: Mainland China Main Material: Steel Color: Silver Black Specifications: 5S/6S/7S Size: About 5S 86mm (3.39in) X 86mm (3.39in) X 22mm (0.87in) 6S: 106mm (4.17in) X 106mm (4.17in) X 25mm (0.98in) 7S: 115mm (4.53in) X 115mm (4.53in) X 28mm (1.10in) Net Weight: About 101g/152g/190g Gear Ratio: 5S:11-13-15-18-21T 6S:11-13-15-17-21-26T 7S:11-13-15-17-19-21-28T Note: This freewheel uses a 10-speed tooth profile and is specially designed to compatible with Brompton Folding Bikes. Please use it with a 10-speed or above chain. Due to the different monitor and light effect, the actual color of the item might be slightly different from the color showed on the pictures. Thank you! Please allow 1-2cm measuring deviation due to manual measurement. 1 x Bike Freewheel