Originally posted by ts357 Really, why is that?
It is a genuine pentax converter…
The reason to stay away from teleconverters is that all teleconverters degrade image quality more or less. There are combinations of lenses and teleconverters (mostly long and fast lenses and good quality teleconverters) which work well, but in most cases you get the same - or sometimes a better -- result by cropping and enlarging the photo in post processing.
On the other hand, if it's a cheap one and has an "A" settings or it is an AF one, you can get the glass out from it and have a good macro extension ring from it