The Hozelock AquaStop connector fits 12.5mm and 15mm diameter hoses. The fitting has an internal valve which stops the flow of water when an accessory (such as a spraygun) is disconnected. This saves having to go back to the tap to turn the water off when switching between accessories, as well as preventing water being wasted.All internal parts are made from ultra tough engineering plastics for a long leak free life.Waterstop connector fitting for 12.5mm & 15mm hose, this fitting is best used at the gun end of a hosepipe.