Material: Typically crafted from high-quality zinc steel, iron, or alloy for the housing, with a nylon or steel wheel for durability and silent operation.Load Capacity: These rollers are often designed to support weights of at least 35KG to 50KG per set.Adjustability: Many models feature a screw mechanism at the top for height adjustment, allowing for precise door alignment.Smooth Operation: Engineered with ball-bearing centered wheels to provide a quiet, frictionless glide, eliminating squeaks.