This single horn in F offers beginning students an opportunity to learn the F side of the horn before advancing on to a double horn. Key of F. Standard .468" bore with a 12.25" bell offers a very centered pitch for beginner players. Director Single Horn In F. This Advanced, Standard Model Horn Is Durable And Well-Braced. Excellent Sound And Response. All Rotors And Bearings Are Tapered For Long-Lasting Performance. .468" (11.89Mm) Bore, 12" (305Mm) Seamless Yellow Brass Bell With Small Throat, Clear Lacquer Finish, Original Conn #2 Mouthpiece, Deluxe Hardshell Case.