These are high grade Bolt Carrier Groups Made in USA.
Bolt is made Carpenter 158 Mil-spec from Major Military Contractor
Gas key is machined out of bar stock, chrome lined phosphate coated, and secured with grade 8 fasteners and staked per mil-spec.
Bolt carrier 8620 and is phosphated outside and chrome lined inside.
Chrome Lined Carrier, Chrome Lined Gas Key, Gas Key Hardened to USGI Specifications, Gas Key Grade 8 Hardened Fasteners, Gas Key Staked Per Mil-Spec, ∙ ∙ Tool Steel Extractor, Extractor Spring.