MATERIALS: The rolling gate wheel is made of high quality PU anti-corrosion steel, sturdy and durable, it has the characteristics of anti-oil, anti-corrosion and anti-rust DIMENSION: The total mounting height is 25.5cm; the wheel diameter is 5cm; the mounting plate is 7.5 × 4.5cm (L×W) LOAD CAPACITY: The maximum load capacity of each caster is 50kg SPRING-LOADED DESIGN: The retractable gate wheel allows 6cm of vertical movement, automatically adjusting the height on uneven ground to prevent sagging, while ensuring that the gate remains in contact with the ground when you open and close it easily and smoothly EASY TO INSTALL: Comes with 4 bolts, heavy duty universal mounting plate with 4 holes fits wooden garden gate, driveway gate and yard fence