MATERIALS: The sliding gate wheels are made of high quality galvanized steel, sturdy, durable, corrosion resistant and waterproof for long time use SIZE: The groove wheel diameter is 50mm, the inner width of the wheel is 20mm, the outer width is 30mm, the groove depth is 8.95mm. Fits 90 degree V track (please confirm the V track size before ordering) LOAD CAPACITY: The bracket thickness is 3mm, which allows 300kg capacity per caster for easy door carrying ROLLER BEARING: Double roller bearings glide stably and smoothly, making the door push effortlessly PERFECT FOR: Heavy Duty Sliding Door, Factory Door, Dog Door, Garage Door, Garden Door, Driveway Gate, Inverted Track, Industrial Machine Track Project Size:4 Pcs Our V-groove steel wheels are made of high quality galvanized steel, which is sturdy, durable, corrosion resistant and waterproof. It is easy to carry heavy objects and the load capacity is 300kg per caster. It is perfect for sliding doors, factory doors, dog doors, garage doors, garden doors, driveway gates, reverse tracks, industrial machine track projects. Specifications: Material: Galvanized Steel Loading Capacity: 300kg per caster Wheel Diameter: 50mm Wheel Inner Width: 20mm Wheel Outer Width: 30mm Groove Depth: 8.95mm Groove Width: 3mm Frames Size: 68 x 38mm (L x W) Bracket Thickness: 3mm Hole Distance of bolts: 55 x 24mm (L x W) Package Content: 4V Groove Casters Delivery Quantity: 4 pieces