These connectors are perfect for reducing 16mm pipe down to 6mm pipe, when using large systems. They are inserted in-line at the point where an AQUAvalve or aquaPot is positioned. They provide a water tight connection unlike many other types of reduction fittings.  They work in exactly the same way as the 16mm to 6mm cross connector but this fitting has one connection for 6mm pipe whereas the cross connector provides two connections for 6mm pipe.