Revolutionary! You can tailor degrees of muffling and attack without having to remove the single-ply, 10-mil bass drum head! The EMAD System consists of two interchangeable damping rings of varying width. In seconds, you can switch from one to another. Fine-tune muffling and pedal response between songs! The MAD maximizes natural attack characteristics and offers tremendous dynamic range, even at low volume levels.
The new coated version adds a little warmth and body and enhances the fundamental note of the drum.
 "Evans Drum Heads - Evans EMAD Bass Drum Heads")