The end fittings are 3/8 BSP male to 1/2 BSP male . See our other listings for other sizes and couplings  If you are unsure of your thread please use the chart below and measure. Inside dia of             size of thread          outside diameter  Female thread                                               of Male thread 8.7mm                 =        1/8" bsp          =       9.3mm 11.5mm                =        1/4" bsp          =      12.9mm 15.2mm               =        3/8" bsp         =      16.2mm 18.8mm               =        1/2" bsp         =      20.7mm 24.6mm               =        3/4" bsp        =      26.2mm 30.4mm              =        1" bsp              =      33.0mm