I was given a 2X KAX Macro TELEPLUS MC7 and thought I should try it out with my DA 50mm f1.8 as it indicates that is the focal length that should be used. It was given to me by my cousin and it belonged to her father.
It works fine in Manual mode and AV. Of course, it did not come with a manual but I think I have figured what the markings on it mean. It is extendable and will provide a 1:1 image.
The first image was hand held and was a tad soft so the second and third images were taken using a SLIK Mini-Pro III tripod. I am fairly sure that my Tamron 90mm Macro could probably do better but I think that this old device has acquitted itself pretty well. It was worth giving it a try. There are quite a few posts in this forum discussing its use.
f3.5, 1/50 sec, ISO 100.
f16, 1/5 sec, ISO 100, about 1:1
f16, .4 sec, ISO 100, about 1:1