I have two of the Gen 2 versions that take Glock mags. It is a fantastic rifle. Is the one you are looking at a Gen 1 or Gen 2? If it is a Gen 2, it will have an M-lok rail with slots in it, where as the Gen 1 has a waffle patterned plastic hand guard.
The Gen 2s has a larger ejection port, better sights, and the better rail. They shoot really well, but you may want to invest in a cheap rubber cheek rest as the cheek rest is metal and isn't great in the cold on your face. You can get the rubber cheek guards on Amazon pretty cheap.
You literally can fold this gun, or open it back up in a second. Best backpack gun you can find that is not a pistol or SBR.
The plastic parts are only on the stock, frame, etc. But there is a lot of metal reinforcements similar to a Glock. It has a lifetime warranty so buy with confidence as Keltec has always taken care of customers.