The Full Force II single ply, medium weight Resonant bass drumhead feature an acoustically “vented” muffling ring tucked into the hoop on the underneath side of the head. The muffling ring helps control overtones and features vent holes along its perimeter that allow the ring and head to move as one. A free PortHole is included with every Full Force II head and allows the drummer to place a 5" vent hole in the desired location.