Figure 1002. These unions are available in 1 thru 4 inch 10,000-psi and 5 and 6 inch 7,500-psi NSCWP. These unions also have a resilient nitrite seal ring (5-inch and 6-inch have nitrile o-ring). They are made from alloy steel and are used primarily by service companies in applications such as cementing, fracturing and acidizing. Designed for high-pressure systems, including truck- mounted systems, Fig. 1002 unions also are available as non-pressure seal unions, and in butt-weld Sch. 160 or XXH, or prepped for sour gas service.