These are the work horses of the trombone family.  Often called tenor-bass trombones in days past, they can do it all throughout the entire range of the instrument.  Compared to the small bore trombones, these models have larger bore hand slides, larger bells, and most have an F-attachment for technical agility and extended range.  If you want one trombone to do everything or you're looking for a professional instrument in the classical music realm, one of these may fit the bill.