All the classic details of the time honored original are reproduced in today's semi-auto Thompson. The frame and receiver are machined from Aluminum Alloy. Walnut Grain Polymer Furniture. This .45 caliber carbine features a 16.5" finned barrel with a compensator.Barrel: 18" Finned O/A .45 ACPLength O/A: 41"Material: Aluminum AlloySights: Pinned in Front Blade Fixed Battle RearStock: Walnut Grain Polymer FurnitureWeight: 8.05 lbs (w/o Magazine)