Miraphone 186-4U BBb tuba. 4 rotary valves, lacquer finish, with nickel silver leadpipe and nickel silver wreath on the bell. This is the true gold standard for professional BBb tubas and is the first choice of fine concert bands everywhere. Known throughout the world for its resounding tone and precise intonation, the 186-4U 4/4-size has long been the standard of comparison for other BBb tubas and is the bestselling all around model among all rotary valve tubas.