The 100rd drum has a diameter of 8.75". Will only fit 1927-A1 Thompson models and Modern Thompson guns made in Worcester, MA. *Note will NOT fit Thompson M1 models (Military version of Thompson-if it has a side charging handle then it is an Thompson M1 Model) and Thompson guns made in West Hurley, NY or before 1990. Each drum is shipped with a drum installation device (3rd hand. Each authentic drum is entirely U.S. manufactured to the exact specifications as the originals.
Specifications:

Caliber	45 ACP
Capacity	100
Finish	Black
Model	SMG
Material	Steel
Type	Drum
Model Fit	Thompson
Brand Fit	Thompson
Max Capacity	100