Description:--Adhesive design, installed on the bottom box, no complicated process.--Caster rotation and precision ball bearings in the shaft make rolling easier. The internal bearing of the wheelchair foot rolls quickly, the surface is smooth, and it will not be jammed by crumbs, hair, and sand, and you will enjoy smooth and quiet movement.--With unlimited durability and high shock absorption. These spare casters allow you to roll smoothly and quietly without making harsh noises, and ensure that you dont scratch or leave marks on any surface.Storage Box Pulley--Scope of use: The wheels are suitable for different types of storage boxes, making it easier to move.Specifications:Material: ABS, double-sided tapeSize:4.7*2.4*1.8cmLoad-bearing: 8KG (when 4 are used simultaneously)Package included:Storage Box Pulley � 1(4PCS)