Produce specification: Made of PVC material , can be used drinking water , sea water , liquids , transport design for easy observation of internal fluid state. The flap design can be installed vertically or horizontally, with reduced resistance, flexible switch, excellent sealing, and can effectively reduce working noise. It is suitable for backflow of water supply pipes, backflow of fish tank pump pipes, backflow of sewers, etc. Inner diameter: 25mm Nominal diameter: 20mm Material: PVC colour: As shown Package Contents: 1 x Check Valve Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.