I think it's based on a existing foam dart molding. It's not going to be good. there is no room for one of the existing versions of airsoft gearbox so it's going to be proprietary. I still don't care I'll buy one and carry on with my 3d printed GBB project. I have several real steal parts, folding stock, trigger guard, heat shield, mags and old maruzen springer gas block, a file for the receiver and learning fusion 360 to design bolt and hop unit mount (think of using a VFC AR hop).