1. Product packaging: 2 auxiliary wheels, 2 shoulder screws, 2 nuts, 2 washers, 2 lock nuts, 2 armrests, 1 key. 2. Good quality: The bicycle auxiliary wheels are made of metal, plastic and rubber. 3. Unique design: Customer safety is a priority. The fitness bike has a small support, which offers more stability and can assist young students in riding before they gain a sense of balance in cycling. So, there's no need to overly worry about your child's safety. 4. Suitable wheels: The wheels are anti - slip, wear - resistant and stable. The support wheel has a thickness of 3.0 mm, providing more safety and stability for beginners. The black wheels can match bicycles of various colors. 5. Universal and adjustable: The support wheels are suitable for 12/14/16/18/20 - inch single - speed bicycles with horizontally backward - facing fork ends. They are not appropriate for semi - recumbent or upright frames.