The Supply Giant 'C' sized arrestor straight water hammer arrestor with an 3/4 inch threaded male NPT connection for residential applications. It is used is to eliminate water hammer, which is caused by water running through fast closing valves, from the piping system. It can damage the seams and couplings, which might result in leaks. The design is lead free and is approved by NSF. Copper Straight Water Hammer Arrester can be soldered to copper fittings, its male sweat connection is also compatible with Push-Fit and Press-Fit fitting systems. ⚠ California Proposition 65 Warning: This product is known to the state of California to cause cancer, or other reproductive harm. For more information, go to www.p65warnings.ca.gov.