This item does exactly what it is supposed to do, without any loss of image quality as far as I can tell. It is actually just a hollow tube - no glass involved. I haven't tried it with all of my lenses yet, but it works great with my macro lenses, allowing focus at very very close distances so that you can really fill the frame with small subjects. One thing to remember - depth of field gets very narrow the closer you are to your subject, so with an extension tube, you need to be extremely careful with were you focus and your chosen aperture. Another thing to bear in mind that others have also mentioned - you can't focus anywhere near infinity with this mounted to your camera. Because I always shoot weddings, etc. with multiple cameras, I envision using this primarily with existing macro lenses for dedicated macro work. But if you don't have a macro lens yet, this is a great way to enter the realm of macro photography.