Rath R4F Tenor TromboneThe large bore R4 is available with an F valve section and is designated as R4F. Michael Rath also offers the R4 and R4F models with in slide tuning. There are three valve options available for Michael Rath Custom trombones: the Ren Hagmann valve, the Willson Rotax valve and the Voigt valve. 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