Need to reduce the thread size of a 9/16" male Threaded Scuba Regulator Low Pressure Hose to 1/4" Male Thread? XS Scuba's Stainless Steel 9/16-18 male to 1/4" male NPT Adapter can make this work. Adapter allows you to attach a standard scuba regulator LP Hose second stage end to smaller threaded requirements with a durable and corrosion resistant stainless steel constructed adapter.