"First off, the whole product is not metal. The shell is, but the part that feeds the bbs is not. Inside of the adaptor is a plastic part that curves the bbs into the ak's tube for feeding. This whole plastic piece can be pushed out through the top, but not the bottom, so it is secure. However, that plastic piece will need to be sanded. Whenever the mag is inserted (I used a dboys midcap, jg highcap, src pmag mid cap, and a jg m16 VN midcap) it pushes that plastic piece up a little ibt, not allowing the adaptor to fit into the ak magwell. So the top has to be sanded to work.
I put this in a JG AK with a full metal receiver, and had to sand it. Tried it in a cybergun spetsnaz, and it fit decently. However, the next problem with this product arises: the magwell inside is a little too big. Had to tape the inner walls to get the mags to stay in with minimal wobble, but front to back wobble can never be eliminated.
Then the next problem arises. The mag catch (the little square on the inside that fits into the m4 mags side hole) is too small, and doesn't go far enough. So your mags have to be held in to feed, and any bumps on the oversized mag release can free your mag.
Bottom line: Excellent idea for a product, but it requires a LOT of modification to work correctly. The trademarks on the side are cool. If you need to, the mag adaptor should be able to be taken out of the magwell without any tools to go back to using Ak mags in a pinch."