Marcus Bonna Case for Detachable Bell Bass Trombone MB-2 - Black NylonImages for Demonstration Purposes. Actual case is in Black Nylon. This model fits a bass trombone with a detachable bell with or without rotary valves. The bell, with a maximum size of 10. 5 inches, is stowed under a foam bell protector. The slide is stored in an external bag on the lid. Accessories can be stored in a compartment inside. The small size can be a benefit while traveling with aircrafts because it fits easier in small compartments. The