The Gibraltar SC-GPHCUT bass drum head port hole cutter lets you cut perfect circular 4" and 6" port holes into your bass drum's resonant head, just like a professional drum tech. A metal tack pokes a hole into your head and secures the cutter and head when you turn the hole cutter. A circular blade then cuts the head as you spin the hole cutter. It's just that easy! Best of all, you can remove the tack and move it to any of nine hole spaces, allowing you to change the diameter of the port hole.