These press tube fittings are suitable for refrigeration applications. Also referred to as ACR (air conditioning and refrigeration) fittings, they crimp onto tubing and have a sealing O-ring to ensure a secure, leaktight connection.Straight connects tubing or pipe in a straight line.Coupling connector type joins tubing of the same connection type, size, thread type, and gender.Press end connection type crimps onto tubing or pipe using a crimping tool and seals with an O-ring for a permanent connection with a compatible copper tube size (CTS) or pipe size.Rolled Center Stop has an indentation around the fitting circumference at its midpoint to prevent the ends of tubing from going deeper than half the fitting's length.HNBR O-ring material is a synthetic rubber (hydrogenated nitrile butadiene rubber) that resists oil, fuels, coolants, and industrial chemicals.Copper fitting material is a corrosion-resistant, malleable metal.