Features Key of BBb.687" bore26" bellOversized braces; extra large caps and guardsOptional case available Description Product Description The 2350 has been the mainstay of King sousaphones for many years. Built with oversized braces and extra large brass caps and guards for extra protection and durability, the 2350 is designed for many years of dependable use. This sousaphone features a .687-inch bore that offers a rich, resonant tone with excellent projection and volume.