50-Rd. Auto Ordnance Ammo Drum for the Thompson Submachine Gun. A Thompson just isn't a Thompson without the most famous accessory item ever - the Drum Magazine! Each authentic Drum is entirely U.S. manufactured to the exact specifications as the originals.The 50-rd. Drum has a diameter of 6 3/4". Each is shipped with a drum installation device (3rd hand) and a Thompson manual.Order ONLINE Today!