KEEP YOUR CHILD SAFE AND CONFIDENT - These 3mm thicker training bike training wheels feature extra reinforcement clamps to create a robust triangular design that helps learners develop a useful sense of balance on the bike and prevents children from worrying about falling off their bikes. High-Quality Flashing Wheels - Non-slip, wear-resistant, and stable. The training wheel support arms are 3.0mm thick, making them safer and more stable for beginners. The black wheels are perfect for any colored bike. UNIVERSAL AND ADJUSTABLE - Support wheels fit 12/14/16/18/20 inch single-speed bikes with horizontal rear dropouts, but do not fit semi-horizontal or vertical dropouts. Cannot be mounted on bikes with gears or derailleurs. EASY TO INSTALL - Includes 2 vertical support arms, 2 wheels, 4 nuts (2 spare nuts), 1 screwdriver, 1 wrench, 1 bicycle bell. Go and enjoy your first outdoor bike ride with your children. Installation - 1. Fasten the training wheel and support rod together. First, install the screws, training wheels, spacers, support rods, and nuts in sequence, then secure with a wrench. 2. To secure the block, remove the rear axle nut from the bicycle wheel and attach the pointed corners of the block to the frame. 3. According to the size of the bicycle wheel, select the appropriate hole position on the support rod. The training wheel should be about 0.5-1 cm (1/5 to 3/5 inch) above the ground. Tighten the axle nut with a wrench. Material: Metal Color: Red, Purple, Green, Blue, Black, Pink Size: 12-20 gimbal mount Package List: Bicycle training wheels*1