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; wheel diameter is 5cm; the mounting plate is 7.54.5cm (LW) LOAD CAPACITY: The maximum load capacity of each caster is 50 kg TOP DESIGN SPRING: The gate's retractable wheel allows for 6cm of vertical movement, automatically adjusting the height on uneven ground to prevent it from sagging, while ensuring the gate stays in contact with the ground when you swing it open and close easily and smoothly EASY TO INSTALL: Comes with 4 bolts, sturdy universal mounting plate with 4 holes to fit wooden garden gate, driveway gate and at the yard fence