The FMK Firearms AR1 Extreme AR-15 Multi Caliber Lower Receiver delivers a lightweight yet robust foundation for your next AR-15 build. Constructed from a high-impact proprietary composite polymer, this stripped lower is engineered to handle multi-caliber setups while keeping weight to a minimum at just 4.3 oz. Its mil-spec dimensions ensure smooth compatibility with standard AR-15 components and uppers, giving builders a dependable starting point for a custom rifle. Designed as a dedicated rifle lower, the AR1 Extreme is ideal for shooters who want a durable, easy-handling platform for range use, training, or general-purpose sporting applications. The polymer construction helps reduce overall rifle weight without sacrificing strength, and the receiver is compatible with most AR-15 lower parts kits, grips, and stocks. Backed by FMK Firearms’ commitment to innovation and quality manufacturing, this lower receiver is built to support a reliable, long-lasting AR-15 build. Key Features:

• Manufacturer: FMK Firearms
• Model: AR-1 Extreme AR-15 Multi Caliber Lower Receiver
• Caliber: Multi-caliber (.223 Rem/5.56 NATO compatible)
• Action: Semi-auto (when built with compatible upper and parts)
• Product Type: Stripped lower receiver
• Size: Mil-spec AR-15 pattern
• Weight: Approximately 4.3 oz
• Compatibility: Accepts standard mil-spec AR-15 uppers and most AR-15 lower parts kits, grips, and stocks