The Evans EMAD Heavyweight 18" Bass Drum Head is a 2-ply bass drum head with two identical plies of 10mil film. The EMAD Heavyweight series provides maximum durability and a compressed attack while maintaining a wide dynamic range. The EMAD Heavyweight 18 inch Drum Head contains two interchangeable damping rings that maximize attack and low-end without removing the head or reaching inside the drum. The unparalleled industry standard Externally Mounted Adjustable Damping (EMAD) system allows the player to adjust attack and focus.