TOOGOO(R) 5 Pcs Fish Tank Round Base Bubble Release Maker Air Stone Black Gray Product Name : Aquarium Airstone;Color : Gray, Black Material : Mineral Stone, Plastic Outlet Hole Size : 4 x 2.5mm/ 0.16" x 0.1"(OD*Inside Dia.) Weight : 99g Package Contents : 5  Aquarium Airstone