Safety assistance function: child safety is the 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 high-strength 3MM carbon steel material. a stable ride 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 training wheel on the rear wheel of the bicycle to adjust the distance between the vertical support and the ground. If you have questions. please . our professional customer service will answer all your questions. General Size: Our training wheels are suitable for bikes from 18 to 24 inches. meeting the needs of children learning to ride in different periods and providing them with safe support. Compatibility: Our products are suitable for children"s bicycles and variable speed bicycles. 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 are about 0.6-1cm high from the ground (installation tools are provided by yourself).