Integrated spring design: Innovative integrated spring design, extends the life of the spring while providing a more beautiful appearance. The built-in spring clamp acts as a shock absorber when wooden gate wheels roll over uneven or rough surfaces, reducing stress on gate hardware and extending the life of a gate posts and hinges Spring-loaded gate caster: adjustable spring-loaded support with spring-loaded vertical travel of up to 4.5 cm, automatic adjustment of the gate height with surrounding terrain throughout the opening and closing cycles, prevents effectively gates from sagging to keep the fence line level Heavy duty gate caster: Thick matte black plated steel plate and double ball bearing bring strong load bearing, capacity Maximum load of 99.8 kg for each gate wheel, making it easier to open or close large heavy wooden gates, vinyl gates, metal tube gates or metal swing gates 360 Swivel Caster: 4 inch aging resistant rubber caster with 360 rotating top plate, excellent mechanical strength and load capacity, easily turns to any direction you want, allows you to spend little force to move the door safely Easy to install: Heavy-duty universal mounting plate with 3 holes to easily attach to wooden gates with lag bolts. The versatile hole pattern also allows for easy mounting to a tubular farm gate along a horizontal or vertical gate rail, with mounting bolts and screws included