Material: Steel Bracket & Rubber Wheels Great Helper: These stabilizers designed for road practices, help beginners gradually learn how to balance on a bicycle Safe & Stable: The 3mm thick steel bracket arms will be more security and stability for bike beginner Suitable for Most Bike of 12 to 20 Inches, comes with parts, theyre individually adjustable & easy to install For Single Speed Bikes Only, please check that these training wheels are compatible with your bike. Training wheels are additional wheels mounted on the rear wheel to maintain the balance of the bike. It is a good helper for bicycle beginners to reduce their fear and gradually learn to keep the bike in balance. How to install bike training wheels? Step 1: Connecting the training wheel and support bar together. First assemble the bolt, wheel, gasket, bracket arm and nut in order and then fix them by wrench. Step 2: Unscrew the bicycle rear axle nut, then fix the stop block, fasten the pointed horn of stop block on the bike frame. Step 3: According the size of bike or wheel, choose the proper hole location on the support bar. Fix them with nut by slightly press strength. Step 4: Using the same way to install the training wheel of the other side. In order to install it smoothly, please screw in press strength. Note: Check that these training wheels are properly tightened before each use. Specification: -Material: Steel & Rubber -Color: Black -Size: Wheel: 4.33 inch*4.33 inch*0.98 inch /11cm *11cm*2.5cm Bracket Arms: 10 inch*1.1 inch / 25.4cm*2.8cm -Fit: 12/ 14/ 16/ 18/ 20 inch Bicycles, not for variable speed bicycle Package Includes: 2 Wheels 2 Bracket Arms 2 Shoulder Bolts 2 Locking Nuts 2 Stop Block 2 Gasket Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.