Features:Made from GPPS plastic material, good waterproof performance.The main function of the check valve is to stop the water from returning back to the tank or pump and keep it in the line.The 20mm tube part is for connecting the water hose and we suggest a hose clamp sealing. (Hose clamp is not included here)Widely used on the water pump, water tank in your home and garden.Notice: This item is only used for water, but not suitable for oil or gas.Specification:Color: Red, ClearMaterial: GPPS plasticTube Inner Diameter: 17mm / 0.67"Tube Outer Diameter: 20mm / 0.79"Overall Size: 25x74mm / 0.98"x 2.91"(D*H)Package Content: 2 x Check Valve.