EVANS HD (Heavy Duty) Dry batter heads balance durability and sonic response with advanced overtone control provided by precision-drilled dry vents. HD Dry heads are made with a coated outer ply of 5mil film and an inner ply of 7.5mil film, plus a 2mil control ring on the underside of the head and dry vents around the perimeter to eliminate stray overtones. HD Dry heads have a semi-defined attack, with short sustain and a bit less brightness than standard HD heads. This coated head also features Level 360 Technology.