Feature: 100% Brand new and high quality. To prevent water backflow to damage the front end of the pump or other products and equipment. After the addition of the stop valve, the pump can be placed above or below the surface of the water to prevent the risk of Water backflow when the pump is shut off. Each outlet needs to connect a stop valve, two-headed pump needs two stop valves, and so on. Description Material: Plastic Color: Blue Overall length: 36mm / 1.42in, the diameter of the middle circle: 8mm/0.31in Two ends: inner diameter: 3mm/0.12in, outer diameter: 4mm/0.16in Suitable for common air pipe(innner diameter approx. 4mm/0.16in) Note: The OUT surface is air outlset, and the other side is air inlet. Package Included: 5PC Valves Note 1.Our size are Asian Size,1-2 size smaller than euro size,please choose your size according to the size chart. 2.Due to the hand measurement, there have size error about 1-2 cm.Item color displayed in photos may be showing slightly different