The MIFA's frame is manufactured by Flying Pigeon. In fact if you go to their website, you'll see a red MIFA.
Your solution for a slipping seat post is quite simple. Now I was told by a bike shop employee some time ago that it is better to use alloy shims instead of the plastic one. There is better adhesion metal to metal.
I'll look into all the possibilities.
Thanks again for posting.
Edward
Originally Posted by
MadArnie
My MIFA folding bike has the exact same frame. MIFA gets it's (unpainted) frames from China or Taiwan and does the rest in Germany.
I think my frame is made without magnesium, but it's still not heavy. Around 13-15kg.
My plastic shim broke and I lost it. I fixed the problem by wrapping ducttape around the seatpost. That solved the problem for me entirely and the seatpost isn't sliding into the frame anymore.