Excellent service with very quick delivery.
I've tried this on Canon's 100 macro, 70-200, 100-400 and 24-105 and it works with all of them, perhaps most surprisingly with the 24-105 bearing in mind that it is designed for use with lenses over 100mm. Yes it can sometimes hunt a bit if trying to use AF on some subjects, but fine once switched to manual.
A great piece of kit to carry in the bag all the time, it takes up so little space, ready for use with any of the above should that extra 'reach' be needed.
Highly recommended and a much cheaper way to get a long lens than spending hundreds - I certainly wouldn't be thinking of buying a 800mm lens with its near 5 figure price tag, although I am sure the quality of the images using such a beast would be better. The quality may be reduced a little, but for most users this is not going to be an issue.