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 50 Rd. drum has a diameter of 6 3/4". Prohibited by state laws in CA,MA,MD,HI,NJ,NY. Works in most full auto models.