Jacob Grey Firearms 9mm 6in Complete Upper Assembly Black. DISCLAIMER: Firearm specifications are subject to change at any time based on availability and supply chain shortage. Specifications for Jacob Grey Firearms 9mm Complete Upper Assembly: Manufacturer: Jacob Grey Firearms Caliber: 9mm Luger Barrel Profile: Medium Taper Barrel Twist Rate: 1-10 Threads per Inch: 1/2x28 Handguard Type: Free-Float Muzzle Device: Brake Finish: Class III Type 2 Hard Coat Anodized Color: Black Fabric/Material: 7075-T6 Gas Block Journal Size-Diameter: .075 in Handguard Style: Round Rail Gun Rail: M-LOK Gun Type: Rifle Gun Make: AR Platform Gun Model: AR-9 Barrel Material: Chrome Moly Bolt Carrier Group Included: MIL-SPEC Magazine Included: No Charging Handle Included: MIL-SPEC Last Chance: Yes Mount Type: M-LOK Projectile Caliber: .355 Caliber Features of Jacob Grey Firearms 9mm Complete Upper Assembly 9mm Specific Upper receiver with reduced ejection port for smaller rounds; Jacob Greys unique checkering design specific to the JG-9 platform; Designed to match lines with Jacob Grey JG-9 & JG-15 Billet Lower however will fit with any Mil-spec lower receiver; Contains integrated Last Round Bolt Hold Open (LRBHO) technology that reliably holds the bolt open when magazine is empty; LRBHO feature is designed for lowers that accept Glock style magazines Package Contents: Jacob Grey Firearms 9mm Complete Upper Assembly What firearm models does the manufacturer say Jacob Grey Firearms 9mm Complete Upper Assembly is compatible with? The manufacturer says that Jacob Grey Firearms 9mm Complete Upper Assembly is compatible with AR-9Jacob Grey Firearms 9MMB6CUA: 9mm 6in Complete Upper Assembly Black