The From the Anvil Ribbed Cupboard Knob Natural Smooth is suitable for hand-crafted cupboard doors. The overall knob size is 32mm and the projection is 21mm. The knobs are sold individually complete with M4 screw. Natural Smooth Cupboard Knob The knob has a natural smooth finish - this is nautral cast iron, finished with a clear matt lacquer which produces a textured look and feel. This is intended for internal use only, but if used externally in an enclosed porch, it will need to be treated with maintenance wax periodically.