At the core of the Echelon is the Central Operating Group, a serialized fire control system that can be easily removed and installed into different grip modules. This modular chassis increases durability and flexibility for various mission profiles or hand sizes. The 4.5-inch barrel balances shootability with concealment potential, while the black melonite finish provides long-lasting protection from wear and corrosion. Specifications and Features: Manufacturer: Springfield Armory Model: Echelon Gear Pac Type: Semi-Auto Pistol Action: Striker Fired Caliber: 9mm Capacity: 20 + 1 Magazine Description: 3 17 rd. & 1 20 rd. Number of Magazines: 4 Barrel Length: 4.5" Rate of Twist: 1-in-10 Overall Length: 8" Frame: Polymer Frame Stock/Grips: Black Polymer Finish: Black Melonite Finish Type: Applied Finish Sights: FS: Lum RS: Tact. Rack U-Dot Sight Type: Fixed Sights Optics Ready Cut: Yes Included Optic: Viridian RFX11 Green Dot Optic Weight: 23.9 oz. Safety Features: Trigger Safety Case: Springfield Range Bag Additional Info: Central Operating Group Additional Info: VIS Optic Mounting System