Features Lightweight, precision machined aluminum 14mm CCW Threaded Muzzle Cap Fixed barrel does not shift when firing, increasing accuracy 14mm Negative threaded barrel adapter and standard barrel crown included Made for the UMAREX GLOCK17 gas blowback series. The combination of set grub screws and high strength aluminum alloy outer barrel make for a highly stable shooting platform. Choose between a non-threaded outer barrel cap for normal use, or a 14mm CCW threaded muzzle cap for infinite attachments. The outer barrel is also negatively threaded so 11mm positive threaded attachments can slide right in!"Non-recoiling" - What does it mean?The non-recoiling outer barrel sets the inner barrel using 2 grub screws in order to fix the outer and inner barrels together. This creates a stable firing platform and reducing all movement between the outer barrel and slide. Consistent performance, stable accuracy and velocity. Manufacturer: Nine Ball / Laylax Specifications: Material: AluminumCompatibility: Elite Force / UMAREX GLOCK 17 and other GBB Pistols w/ VFC Blowback SystemNOTE: Thread lock adhesive is highly recommended to secure the grub screws on the fixed outer barrel