I play a vintage King 2B which comes in its original 1960s very heavy, bulky and not very practical case, in which the bell section could shift around like cargo on a sinking ship… After a long scouting process I opted for this Marcus Bonna case and it exceeds my expectation. This case and the trombone in it together are lighter and much smaller than the original King case. The case has modular blocks with which you adapt the case to exactly fit your trombone. It is fairly easy and renders a good fit. If you want to carry a different trombone, you readjust these blocks in about two to three minutes time.
There is a storage box for mouthpieces, oil, earplugs etc. There is a removable leadpipe/pencil case in the cover, neatly attached with two snap buttons.
There is no real manual, but for a leaflet which warns you to see a video on how to use the shoulder straps. Most importantly, you should fold the straps three times instead of two, otherwise the straps may suddenly untie themselves when carrying the case on your back.
On the outside is a removable sheet music bag. It is unfortunately not big enough for a A4 ring binder, but it will carry an A4 L-folder with sheet music and a tablet. The sheet music bag has two loops with which you can carry a trombone stand. Added bonus: it is easier to carry the stand in its halfway extended position, so it cannot slip between the rings and you can keep the bell support on the same position. Very practical!
It is a very well designed case, somewhat between a case and a bag: soft and sturdy. It is also the reason why some top trombone brands use Marcus Bonna cases for their instruments. It is expensive but very much worth the money.