Uxcell 10-Piece Aquarium Cylinder Mini Bubble Air Stone, 21mm by 22mm,  Gray Aquarium Air Stone; Stone Size : 21 x 22mm/0.82" x 0.86"(DxH) Connector Size : 5.3 x 2.7mm/0.19" x 0.11"(Outer Dia*Inner Dia);Total Length : 36mm/1.41" Material : Mineral, Plastic; Color : Gray Weight : 140g Package Contents : 10 Pcs x Aquarium Air Stone