Those who are looking for a fine inner barrel for precision shooting for your M14 or M16 airsoft gun, you can check this 500mm 6.04 inner barrel made by Systema which is now available at Firesupport. If that does not interests you, there are other inner barrels that you can find at their website... "New unique to fire support Systema M14 6.04 inner barrel only £45, suitable for M14 or M16."