This multiwall polycarbonate sheet fixing buttons is 45mm in diameter with a shaft the same length as the sheet thickness. Fixing buttons should only be used in the centre of the polycarbonates sheet and running in one line, avoid using the fixings across the width of the sheet as this can prevent the polycarbonate from expanding. When installing a 16mm diameter hole needs to be pre-drilled into the polycarbonate sheet and they need to be at least 50mm from any edge of the sheet. The mushroom shaped fixings are manufactured from injection moulded nylon, which are significantly stronger than some PVC versions on the market. Each pack of sheet fixing buttons contains 10 mushroom shaped fixings, 10 foam sealing washers and 10 stainless steel 2 inch screw.