Roll specifications: Roller material: Rubber Roll width: 190 mm Roll diameter: 80mm / 60mm Inner sleeve material: Galvanized iron Axle hole: 16mm Holder specifications: Width: 210 mm Height: 75 mm Shaft height: 55 mm Material: Galvanized iron (5 mm) When choosing bolts, take into account the length you need. You can calculate this with the following formula: Minimum bolt length = height of beam where the keel roller comes on + the thickness of the holder (0.5cm) + the nut (1cm) + any mounting plate (0.5cm)