Guns Modify KM G17 Stainless Steel Thread Barrel Set is made specifically for the Tokyo Marui G17. It's made out of CNC stainless steel with a threaded outer barrel with a 14mm CCW thread for a suppressor. There are 2 versions available, KM and LW version. Such a drastically tight diameter inner barrel can potentially afford you great accuracy but the extreme dimensional tolerance means that it is critical you use the appropriate variety of high quality BBs and you regularly clean your barrel as even the slightest grain of debris can create problems when the gap between BB and barrel is so small