Intended for anti-aircraft work, the BREN drum magazine gave the weapon a capacity of about 100 rounds. While giving the BREN a profile similar to the earlier Lewis Gun, the BREN drum uses a windable internal spring mechanism instead of being recoil operated, and was enclosed on the underside to reduce the chances of foreign material entering the feed mechanism. All four drums fit into a green painted hardwood storage case along with a mounting adaptor and other related tools. The drums, adaptor and tools appear to be in good order, but have not been tested. The case shows wear and tear appropriate to age.