This listing is the SIG Sauer SIGM400 PRO complete upper receiver in 5.56 NATO with an 11.5-inch barrel. This listing is for this 11.5-inch 5.56 NATO upper only.

The upper is a drop-in SIGM400 PRO assembly for a compatible AR-15 / M400 lower. It is chambered in 5.56 NATO. The 11.5-inch barrel uses a 1:7 twist and 1/2-28 muzzle threads with a SIG flash hider-compensator. The operating system is direct impingement with a SIG Micro-light gas block. A free-floating M-LOK aluminum handguard is fitted. The receiver finish is black anodized. The complete upper includes the bolt carrier group and charging handle.

This listing is the SIG Sauer SIGM400 PRO 11.5-inch 5.56 NATO complete upper only.

• Manufacturer: SIG Sauer — SIGM400 PRO complete upper 5.56 NATO 11.5 in, SKU WUAM400-11B-PRO, UPC 798681628711
• Caliber / barrel: 5.56 NATO; 11.5 in; 1:7 twist; 1/2-28; SIG flash hider-compensator
• System: direct impingement; SIG Micro-light gas block; free-float M-LOK handguard
• Finish / contents: black anodized; bolt carrier group and charging handle included
• This listing: this 11.5-inch 5.56 NATO SIGM400 PRO complete upper only
• This item is restricted to LE / MIL / first responders only.