The BERP (Buzz Extension Resistance Piece) is a unit which allows you to do mouthpiece practice using your trumpet to hold the mouthpiece in perfect alignment with your chops, as though you were actually playing. The BERP attaches between your leadpipe and mouthpiece and does not have to be removed for normal playing. An adjuster ring allows you to vary the resistance from open to closed. For use on trumpet (will not fit cornet).