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 the wooden gate wheels roll over uneven or rough surfaces, reducing stress on the gate hardware and extending the life of a gate's posts and hinges Roulette Spring-Loaded Gate Support: Adjustable spring-loaded support with spring-loaded vertical travel up to 4.4cm, automatically adjusts gate height with surrounding terrain throughout open and close cycles, effectively prevents gates from slipping sag to keep fence line level Heavy Duty Gate Caster: Thick matte black plated steel plate and dual ball bearings provide strong load support, 220 lbs maximum load capacity for each gate wheel, which makes it easy to open or close large heavy wooden gates, vinyl gates, metal tube gates or metal swing gates 360 swivel castor: 4" aging-resistant rubber caster with 360 rotatable top plate, excellent mechanical strength and load-bearing capacity, easily turns to any direction you want, let you spend little force to move the wheel safe door Easy to install: : Sturdy universal mounting plate with 3 holes to easily attach to wooden gates with lag bolts. Versatile hole pattern also allows for easy mounting to a tubular farm gate along a horizontal or vertical gate track, with mounting bolts and screws included