High Efficiency, Full Blowback System with Locking Slide; External Hop-Up Adjustment Through Recoil Guide Rod; Aluminum X Series Slide with Optics Cut Accepts SIG AIR Reflex Sight; Ambidextrous Thumb Safeties, Slide Catches and Reversible Magazine Release; Durable Nylon Polymer X Series Grip Module with Picatinny Accessory Rail; 21rd Green Gas Magazine Included; Also Compatible with M17 Series CO2 Magazine; X Series Flat Trigger with 90 Degree Break; Realistic Field Stripping