A reloader never knows when a part might break. Be prepared for anything with high quality factory replacement parts that will have your Thumler's Tumblers Model B cleaning brass like the day it was new. Barrel Inner Dimensions: 8" x 7-1/2" x 6-1/2"Fits: Thumler's Tumblers Model B Barrel Notes: This is the same barrel that comes with the Model B. Extra barrels are helpful when using different types of media so you do not have to swap media back and forth