I bought some (probably not the same brand) years ago from my 2006 50 Summicron & 90 Elmarit. Worked as advertised. No focus, mounting, or locking problems. Hardest part was painting the indents to look nice. However my M8, and then M9, had no problem reading the lens length.
I also have one that is a [email protected]
to M mount that I coded for a Canon 35mm /2