BBb, all brass, .687" (17.45mm) bore, 26" (660mm) bell, bright silver plated finish, 24AW mouthpiece. This all- brass sousaphone is renowned for its tone quality, projection & volume. Built with oversized braces & extra large brass caps & guards for extra protection & durability. Bell screws are attached to a large flange for maximum security. 24.2 lbs., Full warranty.