Description: 100% brand new and high quality. Increase oxygen levels, lower CO2 and raise pH. It is an important instrument to successfully keep aquatic fish for respiration process. Durable, washable and sintered by high temperature, different from other air stones. Creates bubbles in fish tank while attached to an air pump. Creates water currents and dazzling underwater scenes. Easy and convenient to use. Specifications: Material: Mineral Stone + Plastic Color: Gray Suitable for inner diameter 4mm soft tube. Size (4size for selection): 40mm /1.57" x 15mm /0.59" (D*H) 60mm /2.36"x 15mm/0.59" (D*H) 80mm /3.15"x 15mm/0.59" (D*H) 100mm /3.94"x 15mm/0.59" (D*H) Note: Due to the different monitors, please allow slight difference with the colors. Package included: 1 x Air Stone (Size base on your selection) .