Made of black heavy-duty steel, it is strong, durable, wear-resistant and corrosion-resistant. The rollers are made of a combination of high quality bearings and nylon wheels with 6mm thick rails to increase the load capacity of the product. Fits up to Two 22'' wide doors; Applicable Door Thickness: 1" ~ 1-3/4"(25mm~45mm); Door Load Capacity: 360 lbs. Track length should be...