Our local photgraphy store has ordered this set of two for me, assuming these extension tubes is what this thread is discussing.
PENTAX - KOOKA OPTRONICS CO.,LTD
But I still didn't receive them so I cannot share my experience and I am afraid I never get them since it takes this long.
So I was looking around again to see if anything else was on the market and I found these:
ArticleGroup
Zwischenringsatz 13/21/31mm für Pentax
It looks allright to me, but if anyone here can provide me a more experienced opinion I would be gratefull.