BB2001 Designed to fit trombones with a cross brace of 3/8 of an inch.
Includes 1 foam kit. Should fit Edwards and Getzen trombones

BB2002 Designed to fit trombones with a cross brace of 4/17 of an inch. Not guaranteed to fit all Bach model trombones. Includes 1 foam kit.

Some brands require a combination of the two bullet braces. You will need to measure to see if the bullet will fit the cross brace and if there will be room for the rod.