The Clamp Post mount with 25mm (1 inch) Ball is designed for wide range clamping. The heavy-duty mount is made of high-strength composite materials with corrosion-resistant stainless-steel hardware. The clamp mount opens to 2.75 " diameter to securely grip roll bars, tubes, handlebars, warehouse carts, etc. The 25mm ball (1 inch) is compatible with 25mm (1 inch) shafts.