Damping spring design:These sliding door wheels,gate wheel castor have a spring design inside, the wheels can automatically adjust the height on uneven ground and,at the same time,ensure that the door can be opened and closed freely,with less noise! Thick material:Gate wheel with spring with high quality alloy material + PU rubber wheel material. The PU rubber material offers a good shock absorption effect,wear and pressure resistant,strong stability. It can be opened and closed freely. Strong load-bearing capacity:Spring loaded gate wheel high-quality metal materials and spring structure, it offers a strong load-bearing capacity, a maximum load of 60 kg. Heavy sliding gate wheels, suitable for use in gates, trolleys, etc. Simple installation:Durable universal mounting plate with 4 holes for easy attachment to wooden doors or along the horizontal or vertical guides of a tubular gate. Various uses:Swivel wheel for gate,sliding gates,storage shelves, trolleys,flight cases,trolleys,tool boxes,speakers,cabinets, amplifiers, equipment racks,various furniture,etc.