Designed with Jessica Phillips of the Metropolitan Opera Orchestra, Backun Eb Barrels have a proprietary cutback allowing you to use Bb reeds on an Eb mouthpiece. These barrels make playing the Eb more enjoyable. Providing true flexibility & a stable centered tone, Backun Eb Barrels allow you to focus on the music, rather than your instrument.40.5, 41.5, 42.5, 43.43, 44 & 45.