Steel Hose Barb Ball Swivel Fitting, Connector, 1/4 Inch Swivel Barb X 1/4 Inch NPT Male End, PK 6, Interstate Pneumatics, Mfr#: FMBS44-D6

Ball Swivel Fittings are used between the tool and air supply hose to eliminate kinking and twisting. It provides a more natural range of motion than the "traditional" hose barb fitting on a hose.
In addition, it provides a greater bend angle (20 degrees to 25 degrees depending on size) and flow capacity than traditional swivels.