I tested this lens attachment as soon as the shipment arrived and was extremely dissatisfied with the results. I paid less than $10, so my expectations were not very high, but I re-packaged this item and I'm ready to print the return label. I also purchased a Zeikos 4.5x lens, and had similar poor results. Zeikos ZE-4558T 58mm 4.5X Telephoto Lens
I purchased this attachment because no manufacturer currently makes a bona fide teleconverter attachment for the Canon EF-S lenses and I thought this would be a reasonable alternative until I purchased a longer lens or lenses that could be used with a teleconverter. I expected some quality loss, because even this cannot be avoided with top brand teleconverters. However, some of my test images were clearly unacceptable.
I tested this attachment with my Canon EOS XSi with both my EF-S 18-55mm lens and my EF-S 55-250mm lens. With the 18-55mm lens extended to 55mm, the images definitely appeared closer, but I cannot say that they were truly 2x closer. The images were not as sharp as the images without the attachment, but the results were surprising respectable. Also, autofocus was not much of a challenge, but I did use manual focus to get the best picture. That said, if this attachment truly achieved 2x that would give you the equivalent of a 110mm lens. The images were clearly not even close to those of my other lens at 110mm, so I would have sent it back simply based on this.
The test results with the 55-250mm EF-S lens were far worse, which I guess would be expected. First, with the lens fully closed to 55mm, the image was partially blocked by the outer ring of the lens attachment. With the lens fully extended, the image turned completely foggy and blurry. In fact, I could not even make out the text on the side of a box that I could clearly see with the 250mm lens alone.
In conclusion, I imagine this lens attachment may be useful in some limited situations, as I demonstrated with my 55mm lens. However, to say that this is a quality product that can be used on even an entry-level DSLR camera (which the Canon XSi is considered) is a major overstatement. I could see how this might be useful on a mid-range point-and-shoot camera that lacked sufficient zoom range. It is clear that any quality DSLR camera has lenses available that would easily exceed the quality of the images shot within the limited range of this attachment, which I demonstrated with my 55-250mm lens. With a high megapixel camera, I would even guess that a cropped image from a 55mm lens would still beat an equivalent photo shot with this 2x attachment.
For those with a DSLR, save your money and buy a better lens that will get the results you are looking for.
For those with a point-and-shoot, save your money and buy a better point-and-shoot.
NOTE: I also added pictures showing my test results. Follow the "See all # customer images" link below the main product picture to see my examples.