One side has the Original Tacky Mat for small nymphs and dries. The other side has the Big Bug Tacky Mat for larger patterns such as streamers, hoppers, stimulators, parachutes, and larger nymphs. Holds 240 flies total. Holds flies tighter and is much more durable with excellent resistance to the elements. The box is a tough polycarbonate that won't warp. Secure latch-free magnetic closure. Slim profile takes up less room in your vest.