These drumheads contain two plies of film, an outer ply of 5mil film, an inner ply of 7.5mil film, and a 2mil overtone control ring on the underside that floats with the head, eliminating excessive overtones and controlling sustain. The HD Dry model incorporates Evans Level 360 Technology for ease of tuning, extended pitch range, and optimum quality of sound.Evans snare side clear 300 heads are the best selling series of Evans snare side heads and feature a single ply of 3mil film. 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. Features One of Evans most popular heads, this single ply reacts with the fat spread of a double ply; made using two plies of film, an outer ply of 5mil and an inner ply of 7.5mil film 2mil overtone control ring on the underside that floats with the head, eliminating excessive overtones and controlling sustain The Dry version features small vent holes around the edge that eliminate stray harmonics and tighten the sound Exclusive Evans Level 360 Technology collar design ensures proper contact between drumhead and drum shell Specifications Treatment: Coated Ply: 2 Thickness: 12.5mil (5mil / 7.5mil) Technology: Dry Vents