There is no such thing. Chinese UFs are cut and stamped out the receiver. The Chinese figured that 1.5 mm metal could do it all. They don't even feel the need for swell neck rivets. Here is a photo of the rear of my MAK before the infamous demill.
Dutchkma, good picture, that explains it. So I geuss that one can't be added to a straight stock? I have not had the chance to handle any Chinese underfolders. They are on the boarder of illegal here in MI
(OAL issues). The only Chinese I see are fixed.
Someone some where was going to try and stuff a Yugo under folder into a MAK receiver. I had advised that person with the same info that I did here. Do not remember seeing a finished result. I'll look through my post history over at Gunco to see if it is there.