Rancilio Complete Expansion Valve, Threaded Connection A complete expansion (over-pressure) valve for the old Rancilio S and Z series, as well as the Millennium model, both ends are threaded, unlike the R_525 which has a barbed outlet connection. SPECIFICATIONS 3/8" male x 1/4" male BSP thread, both connections threaded COMPATIBILITY Fits: Rancilio S series, Z series, and Millennium INSTALLATION Technician-level, plumbed inline on the pump/boiler circuit. PRO TIPS Double-check your outlet connection before ordering, this version has threaded connections on both ends, while the similar-looking R_525 has a barbed outlet for hose. Installing the wrong one means re-plumbing the outlet side.