3/8" x 3/8" Compression Tee, Quiet Pipe, Hammer Arrestor, Helps Solve Current & Potential Water Hammer Problems, Use A Piston Design To Help Absorb The Water Shock In The System, When A Valve Is Closed Abruptly, The Water Moves Into The Pressurized Chamber Of The Hammer & The Water Pressure Is Absorbed To Prevent Banging Within The Pipeline, Once The Water Flow Comes Out Of The Chamber, It Is Dissipated To The Rest Of The Water Line.