Safety Assist Function: Children's safety is most important. Our product weighs 1.1 kg. Sturdy training wheels help kids maintain balance and provide greater safety and stability. Sturdy and durable: The upgraded version of thick 3MM high-strength carbon steel material. stable driving without deformation. The wheels are made of environmentally friendly PVC. non-slip. wear resistant. durable and low noise. Easy to install: Use a wrench to install the drive wheel on the rear wheel of the bicycle to adjust the distance between the vertical support and the ground. If you have questions. please contact us. our professional customer service will answer all your questions. General size: Our training wheels are suitable for 18-24 inch bikes. meeting the needs of kids learning to ride at different times and providing them with secure support. Compatibility: Our products are suitable for children's bikes and variable speed bikes. Install our special extension screws on the side of the shifter. After installation. please make the main wheel perpendicular to the ground, and confirm that the auxiliary wheels on both sides have a height of about 0.6 1 cm from the ground (installation tools are provided by yourself).