Metal slide and outer barrel set for Tokyo Marui Model 17/18 series gas blowback pistols. The set comes with a metal slide and metal outer barrel with 14mm threading to accept silencers, flash hiders and other such barrel extensions.
These sets are available each for the Tokyo Model 17, Model 17 Custom and Model 18C in both black and silver versions (slides vary in colour, all barrels are black).
Threaded barrels are fairly common on 1911 and M9 pattern gas pistols but for the Model 17 series it can be trickier to find. Now you can simply pick up one of these sets to add threading to your pistol.
Although technically multi purpose, threading like this is most commonly used to add silencers. Recent additions of pistol carbine kits to Airsoft also means such threading can be used to add barrel extensions, silencers and flashhiders in order to add more extension options to incorporate longer inner barrels without having to use an unusually long outer barrel.
These slides claim compatibility with normal real pistol holster dimensions and as such should have little trouble fitting your Airsoft and real steel holsters.