A mouthpiece is the end of a pipe from which the smoker inhales. Most mouthpieces involve a hollow tube with an opening at one end, much like a straw. GRAV® mouthpieces come in a variety of forms - from the Helix Venturi chamber mouthpiece that spins and cools smoke as it exits the pipe, to the ergonomic Upline mouthpieces that are pinched to fit between a smoker's lips for greater comfort and a better seal.