The EMAD Heavyweight series features two plies of film. The combination of two identical plies of 10mil film provides maximum durability and a compressed attack while maintaining a wide dynamic range. The EMAD Heavyweight 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. For over 60 years, Evans has been an innovator in drumhead manufacturing and design. As the creator of the first synthetic drumhead and other revolutionary products such as EMAD, Hydraulics, and the UV1 series, Evans drumheads are designed with the intent of solving problems for drummers. Regarded for high quality and consistency all Evans drumheads are made in the USA and feature Level 360 Technology., 20" drum head made using two identical plies of 10mil film, Externally Mounted Adjustable Damping system allows the player to adjust attack and focus, Very versatile head for all music genres; a true working drummer's choice, All Evans drum heads are designed, engineered and manufactured in the USA