This training wheel set is designed to provide quiet operation, durable performance, and adjustable mounting for common kid bikes. It combines a thickened PU wheel, broad size compatibility, and secure bearings to support safe and comfortable learning rides. Key benefits - Thickened PU wheel for comfort and stability - Wheel thickness 2.5 cm (0.5 cm thicker than ordinary wheels) helps reduce bumps and absorb shocks. - Quiet, smooth operation with less rider effort, facilitating an easier and more comfortable ride. - Universal compatibility with adjustable mounting - Bracket with 5 mounting holes fits bikes in sizes 12, 14, 16, 18, and 20 inches. - Round, attractive design with a blue color accent that complements various bikes. - Note: Not available for variable speed bikes. - Durable, safe bearings and protective washer - Double carbon steel bearings provide quiet, smooth rotation and longer wheel life. - Enlarged washer covers the entire bearing to prevent misalignment or bearing dislodgement during use, enhancing safety as the child grows. Use scenarios - Learning on 12–20 inch bikes at home, parks, or school routes: install on a smaller bike to stabilize first rides and build confidence without sacrificing control. - Shared family bikes: easy to switch among multiple bicycles within the 12–20 inch range, enabling siblings to use the same set as they grow. - Riding on less-than-perfect surfaces: the thickened PU wheel reduces bumps and fatigue on sidewalks or uneven paths, helping new riders stay comfortable longer. This product combines a quiet, durable wheel with broad compatibility and safety-focused design to support confident, growing riders.