【Heavy Duty Side Parking Brake Bearing】: Adjustable spring assist gate roller, adjust height (0-5.08cm) automatically on uneven ground, free brake to prevent inertia, sag or gate movement. Perfect for farm, estate and home use. Any Roller has a load capacity of 200kg. 【Spring-loaded gate rollers】: The whole roller is made of high quality rubber material and metal structure, combined with double ball shafts, bringing double the load. The spring construction, resilient inertia movement and gate rollers prevent your gate from being dragged around and damaging the patio floor while making the gate easier to open and close. 【Flexible Rotation】: Double ball shafts and 360° rotation in all directions, the caster is supported by heavy-duty bearings with precision steel balls on each side, providing lower noise, less friction and more flexible rolling, easy to open and close and effortless.<p >【Built-in Spring】: This is a newly designed door roller, different from the traditional door theory. The built-in spring can slow down the aging speed of the spring, extend the life of the door wheel and make the appearance more beautiful. 【Universal】: The spring-loaded door wheel features a powerful universal 3-hole mounting plate that easily connects to the horizontal or vertical tracks of a wooden door or a garden gate.