Evans Hydraulic coated drumheads feature two plies of thin film offering maximum durability, and a fat, deep and short sound pioneered by early 70's rock and roll. Unique translucent coating delivers additional warmth, focus, and depth. Hydraulics are famously easy to tune, making them a perfect fix for troublesome drums and players with little tuning experience. Both Red and Blue are 2 plies of 7mil film while Black is 6.5 mil over 7.5 mil.