The M400-SDI X has been developed with the input from the professional instructors at Sig Sauer Academy. Building upon their decades of experience and countless hours of instruction, Sig Sauer has developed the M400-SDI X to meet the highest standards of performance and reliabilty. With fully ambidextrous controls including a bolt catch/release unique to the M400-SDI lower receiver, the M400-SDI X delivers advanced performance for both left and right-handed shooters and makes transitional shooting easier than ever. The free-floating handguard utilizes a new steel lockup design that significantly reduces handgaurd deflection by providing maximum rigidity and allows for accessories to be attached on all four sides with no effect on accuracy. The 2-stage Matchlite Duo trigger provides an out-of-the-box crisp 4.5 - 6.5 lb pull weight with a flat blade design for a precision feel. The M400-SDI X utilizes the highest quality performance coatings to ensure maximum durability and reliability. Moss Green Cerakote Ambidextrous bolt catch and release Compensator/Flash Hider Dual Clamp Handguard Locking System for Reduced Deflection Low-Profile gas block with Mid-Length Gas System Sig 2-Stage Matchlite Due Trigger Magpul SL Stock