Barbed Coupling Valve. Use to connect two sections of tubing with shut-off valve. Valves are great to control, disperse, slow and/or divert water in all drip irrigation systems.Features Simple on-off operation and straight through flow.Green cap for standard irrigation applications.Purple cap is used for re-claimed water.Black cap for general purpose.UV stabilized materials for long life.Applications: Secondary zone water diversion and flow control. Gravity irrigation flow valve. Any situation where fluid restriction is needed.