Great tube but wish I had bought the three tube kit from Kenko.
Wayne

Pros:

You can get much closer
Works with both EF-S and EF lenses
Auto focus still functions perfectly
Takes up very little room in your camera bag
Item looks about 3 times as large in photo using 17-40 Canon F/4 Lens

Cons:

A little tight to put on and take off of lens
Can no longer focus very far away let alone infinity

Review:

I purchased this Extension tube so I could take better Macro photos without having to purchase an expensive Macro lens. I've got so many lenses already.

I installed the tube between my Canon Rebel XTi and Canon 17-40 F/4 L lens and bang!!! Instant macro lens.

A photo I had taken without the tube of a penny using the Canon 17-40 zoomed to 40mm gave a so so image. Putting the tube on allowed me to focus so close the penny filled almost the entire view finder. Looking at the penny image taken with the tube you can see little details I never noticed before like each and ever step and little details like the little FG on the lower right corner on the back of the penny.

Verdict:

I highly recommend it's worth every penny!!!

Good product, does what it says it'll do. I was suprised how well it works.

I received the extension tube(s) a couple of weeks ago, they are wonderful. They work as expected, the AF works perfectly. What is especially great, about the Canon extension tubes is, you can use the EF-S lenses as well as the EF lenses. Other brands will not allow you to do that.

This 12mm extension tube work well with moderate super zoom lens for better close up photography