The NIBCO Press System copper cap features an inboard bead and EPDM O-ring. Simply applying pressure from a pressing tool tightens the O-ring onto the tube, ensuring a clean, watertight seal in seconds with no flame, solder or flux. The cap has a press connection. The fitting is used to fit over the end of pipe to seal the end. NIBCO press fittings are the fastest, easiest way to join copper tubing.