This parts lot is for the San Cristobal Cal..30 Carbine, or machine carbine as made in the Dominican Republic. Not common in the US but seen over much of Central and South America. This design is very similiar to the Beretta 38 series SMG, the diameter of the tube is even the same. You can find the tubing which is 1.500: OD with a wall thickness of about .160 gives you the ID of about 1.150, about the same as 9mm Beretta. Great set of parts to build either a semi or full auto carbine using many items common to the Beretta SMG series. This kit has the complete bolt assembly, ejector and bolt cam area, semi and full auto triggers, sear, rear cap and rear cap lock. There are also 4 of the 30rd US Cal..30 Carbine magazines used by this gun. Pictures show the parts and magazines, detail of the bolt in unlocked, locked and the cam area on the ejector. Also shows the bolt face of the Cal..30 Carbine bolt anda standard 9mm bolt, as well as the carbine bolt sliding into the receiver of a Beretta 38 Series receiver tube. . There are many photos of the complete weapon on the web and in many arms books.