About this item High quality material, made of high-quality iron, easy to install. The surface is chrome plated for rust prevention and longer service life. Expander Size: Easy Fit Stabilizer Extension Bolt, Axle Expander Thread Pitch 3/8-24. Screw Size: The total length of this screw is 35mm, the limit length is 20mm, and the thread length is 15mm. Scope of application: Used to solve the problem of being unable to install training wheels on bicycles with short rear axles. The product includes: 2 extenders and 2 screws.