EBB431 is a 4/4 size four-valve BBb tuba. The fourth valve helps with the intonation, tone and versatility when used in place of the typical one- and three-valve combination. This top-action instrument is ideal for school and community ensembles that perform more advanced literature. It includes these important features: Key of BBb Full-size tuba with 17 1/2" yellow brass upright bell Yellow brass construction with rose brass leadpipe and nickel-silver tuning slides Four stainless steel pistons through a .728" bore "Euphonium-style" top-action valve assembly Exquisitely finished in a clear lacquer Durable, hard-shell ABS case with wheels. Includes silver-plated Eastman mouthpiece