KEEP YOUR CHILD SAFE AND CONFIDENT - These 3mm thicker utility bike training wheels have added reinforcement clips to create a sturdy triangular design that helps learners develop a usable sense of balance on the bike and save kids from worrying about falling on their bikes. High Quality Flashing Wheels - Non-slip, wear-resistant and stable, the training wheel stand arms are 3.0mm thick, these will be more secure and stable for beginners. Black wheels are perfect for any color bike. UNIVERSAL AND ADJUSTABLE - Support wheels fit 12/ 14/ 16/ 18/ 20 inches of single speed bikes with horizontal rear-facing track fork ends, but do not fit semi-horizontal or vertical dropouts. Cannot be mounted on bikes with derailleurs or derailleurs. EASY TO INSTALL - Includes 2 Vertical Stand Arms, 2 Wheels, 4 Nuts (2 Spare Nuts), 1 Screwdriver, 1 Wrench, 1 Bike Bell. Go and enjoy your first outdoor cycling session with your kids. Install - 1. Attach the training wheel and support bar together. First install the screws, training wheels, spacers, support rods and nuts in sequence, and then fix them with a wrench. 2. To secure the block, remove the rear axle nut from the bicycle wheel and secure the sharp corner 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 an adjustable wrench. material: metal Color: red, purple, green, blue, black, pink Size: 12-20 gimbal bracket Packing list: Bicycle auxiliary wheel*1