Duda solar Brass fittings for Duda Solar water heater systems Our Brass fittings use G-type threads. The G-type threads (parallel, no taper) are ideal for connecting to our stainless steel tubing which also uses a G-type thread. Make connecting to your Duda Solar water collectors easy by using our compression fitting adapters to connect to the copper header pipe and convert to the G threads that you need to connect directly to the stainless steel tubing. We have many options for these adapters. Both in ½” and ¾”, male and female threads and compression fittings for easy attaching to the copper pipes on the solar collector. Our ¾” compression x ½” male thread adapter is the most popular for connecting directly to the collector and then to ½” corrugated stainless steel tubing.