Roll specifications: Roller material: Rubber Roll width: 133 mm Roll diameter: 70mm / 48mm Inner sleeve material: Galvanized iron Axle hole: 20mm Holder specifications: Width: 148 mm Height: 80 mm Shaft height: 60 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)