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 stress on gate hardware and extending the life of a gate's posts and hinges Spring Gate Roller: Adjustable spring-loaded carrier with spring-loaded vertical travel up to 4.4cm, gate height automatically adjusts with surrounding terrain throughout open and close cycles, effectively prevents gates from sagging to keep fence line level Heavy Duty Gate Caster: Heavy-gauge matte black plated steel plate and dual ball bearings provide strong load support, load capacity maximum 220 lbs for each gate wheel, making it easy to open or close large, heavy wooden gates, vinyl gates, metal tube gates or metal swing gates Swivel Caster at 360: 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 Secure Gate Easy to Install: Heavy duty 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