The Antoine Courtois AC420BT Legend Series Thayer F-Attachment Trombone offers amazing performance and sound for the player looking for a symphonic trombone. The AC420BT Legend features a .547" bore combined with an 8.5" one piece bell that provides excellent projection and response. The open wrap F-Attachment with a Thayer valve features a responsive, free-blowing design plus an adjustable thumb trigger for player comfort and mini ball linkage for smooth action. The Courtois AC420BT Legend Thayer F-Attachment trombone includes a lightweight contoured case and mouthpiece and is available in lacquer finish with a choice of yellow or rose brass bell. Select from dropdown menu.