solid, easy to use, high quality

Advantages and disadvantages:
+ Metal
+ Easy to install
+ Easily settle (button, as if you would arrange a normal lens then the ring, unscrew the filter thread)
+ Super results
+ Ring is super laid on camera and lens also firmly on the ring (comment below)
- All equipment is turned off (but is known at retro rings and no real shortcoming)

Additional useful features:
+ Flash (internal or external) or sufficient lighting otherwise the subject is too dark
+ Tripod or steady hand - because the focus is very sensitive, but can do without if you have a steady hand
+ Protection Ring for lens in reverse position Canon - really great because you can then screw up even the lens cap again

I was really surprised how great it works with the retro ring. Photographing in itself takes some practice (10 min Eingewöhnzeit), because you have to get very close to the motives, so I sometimes afraid to initiate. But what is actually positive aspect, because you get really close to objects approach with a normal 18mm-55mm lens.

Since many of my predecessors have written in their reviews that the lens was sitting wobbly on the ring I want the here set the record straight - that can be avoided very simply:
I had the same problem at first, but found out that you have to unscrew the ring just right on the lens until it no longer goes on (but without violence). Then the ring lens complex feels firm before being attached to the camera and not wobbly on. However, it could take a few tries before you get the hang of how you have to screw on the ring. By the way, the same principle as in a water bottle because the yes and sometimes not "fit": P

Conclusion:
Buy recommendation for all macro fans and those who want to become who seek cheaper alternative to macro lens and because the value for money is more than exceeded.