A Thompson is just not a Thompson without the most famous accessory item ever - the drum magazine. The impressive look and feel of the drum magazines are unsurpassable. Each authentic drum is entirely U.S. manufactured to the exact specifications as the originals. The 10 Rd. and 50 Rd. drums have a diameter of 6.75". The 100 Rd. durm has a diameter of 8.75". Each drum is shipped with a drum installation device (3rd hand) and a Thompson manual. It works in most full auto models.