unique product combines resistance and the ability to finger notes to the standard practice technique of mouthpiece buzzing resulting in a stronger embouchure, endurance and range.The BERP is the favorite practice aid of 50,000 brass professionals and students worldwide! Clamps firmly onto the open end of the receiver, with the mouthpiece removed. The clamp is designed to tighten around a round, hex or convex shaped opening. On some receivers which have an oversize ring at the opening, it may be necessary to push the clamp past that before tightening down. Most people prefer the Ultimate BERP to be lined up parallel to the receiver at the "three o'clock" position. You may experiment with it in other positions to determine what is best for you. Once the BERP is firmly attached, you can then alternate easily between buzzing and playing your instrument by switching the mouthpiece.