Sig Sauer’s M400 SDI XSeries delivers a rich set of upgrades to one of Sig Sauer’s most formidable rifles. As part of the XSeries, the M400 SDI comes standard with enhanced ergonomics and performance enhancing features. In terms of ergonomics, the M400 SDI XSeries is 100% ambidextrous with the safety selector, charging handle, magazine release, and bolt release being easily accessible on either side of the rifle. The M400 SDI’s maneuverability is further improved by a series of lightening cuts in the upper and lower receiver which reduce weight without impacting performance. To accommodate a maximum customization, the M400 SDI XSeries is outfitted with multiple attachment points. A picatinny rail runs the entire length of the rifle, giving the user virtually unlimited options for optics, iron sights, and clip-on night vision/thermal devices. The fore-end features M-LOK attachment points for accessories such as tactical lights/lasers and grips, and lightening cuts in the top and bottom portions help reduce weight even further as well as vent off the heat generated from firing. The fore-end is coupled to the receiver with steel connection, a proprietary Sig design, that minimizes deflection and increases the rigidity of the fore-end when accessories are attached. Other features of the M400 SDI XSeries include a unique Hybrid Muzzle device, which reduces visible flash signature while also cutting down on muzzle rise. In addition, the M400 SDI XSeries is equipped with a 2-Stage Matchlite Trigger with a crisp 4.5 – 6.5 lb pull for exceptional accuracy and fast shooting. Features of the M400 SDI XSeries:100% ambidextrous safety selector, charging handle, magazine release, and bolt releaseLightening cuts for reduced weight and enhanced maneuverability Full-length picatinny rail M-LOK attachment points Hybrid Muzzle device2-Stage Matchlite Trigger Sig Sauer M400 SDI 5.56x45mm NATO 11.5" 1:7" Bbl Optics Ready Pistol w/Magpul BSL Brace PM400-SDI-11B-BLK