• NOTE: Will not fit bass trombone. Yamaha states this mute will fit tenor or "tenor-bass" trombones. The term "tenor-bass" is archaic and refers to a large bore tenor with an F attachment. This mute will fit all tenor trombones with bells up to 8.5 inches (20.8cm) in diameter. It will not fit true bass trombones with 9.5, 10 or 10.5 inch bells. -cdp