Geissele Bolt Assembly Stress Proof. Each Forged bolt is rigorously inspected high pressure tested mag particle inspected and Nanoweapon coated. Specifications for Geissele Stress Proof Bolt Assembly: Manufacturer: Geissele Color: Black Caliber: 5.56x45mm NATO .223 Remington Gun Make: AR Platform Gun Model: AR-15 Included Accessories: Extractor Package Contents: Geissele Stress Proof Bolt Assembly What firearm models does the manufacturer say Geissele Stress Proof Bolt Assembly is compatible with? The manufacturer suggests that Geissele Stress Proof Bolt Assembly is compatible with AR-15Geissele 05-2991: Bolt Assembly Stress Proof