Integrated spring design: Innovative integrated spring design, extends the life of the spring while providing a more beautiful appearance. Built-in spring clamp acts as a shock absorber when wooden gate wheels roll over uneven or rough surfaces, reducing stron gate hardware and extending the life of a gate's posts and hinges Spring-loaded gate roller: adjustable spring-loaded support with up to 4.5cm spring-loaded vertical travel, automatic gate height adjustment with surrounding terrain throughout open and close cycles, prevents effectively gates from sagging to keep the fence line level Heavy Duty Gate Caster: Heavy-gauge matte black plated steel plate and dual ball bearings provide strong load support, capacity 200 lbs maximum load capacity for each gate wheel, making it easy to open or close large, heavy wooden gates, vinyl gates, metal tube gates or metal swing gates 360 Swivel Caster: 4" aging-resistant rubber caster with 360 rotatable top plate, excellent mechanical strength and load capacity, easily turns to any direction you want, let you spend little force to move gate 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 track, with mounting bolts and screws included.