uxcell One Way Non-Return Check Valve Air Pump CO2 System 6 Pcs for Aquarium Tank Product Name : Aquarium Check Valve;Use for : Fish Tank, Aquarium Hole Diameter : 2mm / 0.08";Fit Pipe Inner Diameter : 4mm / 0.16" Total Size : 52 x 15mm / 2" x 0.6" (L*Max.D);Material : Plastic Color : Clear, Black;Weight : 20g Package Content : 6 Pcs x Aquarium Check Valve