The original gas blowback internal system that ran both the WE PDW and WE SCAR shared the same infamous brass tube across the breech that many considered a breech in realism.
The result was WE releasing an open-bolt version with no brass tube; the WE PDW came out in an open-bolt variant and then the kit came out to covert older WE PDWs into the open bolt system.
Now you can do the same thing with your WE GBB SCAR. Simply open up your WE SCAR, install this kit, and voila you have your open bolt system gas blowback SCAR.
This kit includes a full gas bolt and nozzle group, trigger assembly, hop-up unit, inner barrel, outer barrel, recoil guide, bolt catch assembly and flash hider. The barrel length is the same short type as found on the base model, an 8 inch CQB barrel.