KJ KP-13 CO2SPECIFICATIONS: System : Gas Blow Back Action : Semi auto Velocity : ~ 380 fps with extension Velocity : ~ 320 fps without extension Length : 180 mm Weight : 775 g Hop up : Adjustable Gas : CO2 Capacity : 23 + 1 FEATURES: Aluminum slide, Aluminum outer barrel, metal full size CO2 magazine and all metal internals High Impact Full Black Polymer frame Under barrel 20mm rail for accessory attachment extension inner barrel included to achieve higher fps