KEEP YOUR CHILD'S SAFETY AND CONFIDENCE: This 3mm thickening practical bicycle training wheels add the reinforcing clip to build the sturdy triangle design assists learners to developed a usable sense of balance on the bicycle, avoid children worrying about wrestling because of cycling HIGH QUALITY FLASH WHEELS: Anti-slip, Wear resistant, Stability, training wheels bracket arms are 3.0mm thickness, these will be more security and stability for beginner. Black wheels fit perfectly on any color bike. UNIVERSAL AND ADJUSTABLE: The support wheels fits 12/ 14/ 16/ 18/ 20 single-speed bike inches with horizontal rearward-facing track fork end, but not suitable for those with semi-horizontal or vertical dropouts. Cannot Be Installed On Bikes with Derailleurs or transmission EASY TO INSTALL: Included 2 x Vertical Bracket arms, 2 x Wheels, 2 x Nuts, 2 x Bolts and 2 x Washers Go and Enjoy your first outdoor bike exercise with your children! INSTALLATION: 1.Connecting training wheel and support bar together. First put screw,training wheels, gasket,support bar and nut in order and then fix them by wrench. 2. Fix the stop block, remove rear axle nut from the bicycle wheel, fasten the pointed horn of stop block on the bike frame. 3 According size of bike wheel, choose the proper hole location on the support bar. training wheels should have about 0.5-1cm (1/5 to 3/5in) space from the ground. Tighten axle nut with adjustable wrench.