Product Description Plastic Barbed to BSP Male Valves Male BSP – Barb Valve All sizes correspond to the outside diameter (OD) of the pipe, ie a 16mm fitting is suitable for 16mm OD Hose (13.6mm internal). 5 Sizes Available; 12mm – 1/2″ Male BSP 12mm – 3/4″ Male BSP 16mm – 1/2″ Male BSP 16mm – 3/4″ Male BSP 20mm – 1/2″ Male BSP 20mm – 3/4″ Male BSP