Fast bass damping adjustment without head removal! The Evans Adjustable Dampening EMAD Bass Drum Head comes with 2 damping rings, each of which affects the head's sound and pedal response. EMAD stands for Externally Mounted Adjustable Damping and this external system maximizes natural attack characteristics. It offers tremendous dynamic range (even at low dynamic levels where other systems fall short). It also allows quick, easy adjustments without having to remove the head from the drum an especially valuable feature during recording sessions. If you're recording bass drums, the EMAD will make your life easier. Order today! Evans EMAD series features a 10mil of single-ply film providing an ideal balance of punch, power and low-end. The unparalleled industry standard Externally Mounted Adjustable Damping (EMAD) system allows the player to adjust attack and focus.For over 40 years, Evans has been a pioneer of drum head manufacturing and design.