Marine grade stainless steel screws provide excellent corrosion resistance and are the work horse for modern boatbuilding or exterior woodworking applications. The Round Head has a semi-elliptical top surface with a flat bearing surface underneath. The flat bearing surface allows for lateral movement (as opposed to a Flat or Oval Head that have a countersunk bearing surface that will self-center in the mounting holes) when attaching hardware. Generally chosen for it's traditional appearance.