The Thomann BF-304 Bellfront Baritone is a combination of amazing sound combined with a durable body. The baritone features 4 valves that are used to change the length of tubing of a brass instrument allowing the player to reach the notes of various harmonic series. The body of the instrument is made of brass that ensures excellent tonal output and long lasting durability. The bore diameter of the instrument is 14.50mm.