The Evans Hydraulic Black tom drumhead features two plies sandwiching a thin layer of oil, giving the head an especially fat, deep, and short sound made famous by early-70s rock. The oil decreases sustain, while enhancing attack and low end. Plus, Evans Hydraulic Black drumheads are famously easy to tune, so they're a great choice for troublesome drums or beginning players wanting instant access to great sound.
2-ply head, sandwiching a thin layer of oil
Oil decreases sustain and enhances attack and low end
Easy to tune