Rath R3F Tenor TromboneThe Rath Custom R3F Bb tenor trombone is a 0. 525 instrument that comes with an 8 bell as standard. The medium large bore R3 trombone is available with an F valve section with the designation of R3F. Because of the modular construction of Michael Rath custom trombones, you can remove the valve section and replace it with a detachable gooseneck, available as an option, creating a straight tenor trombone. Similarly, if you already own a straight R3 or