Summary: This hood should have been supplied with the lens as purchased new. It works great and all, but Canon should have supplied it with their lens. They supply lens hoods for their other expensive lenses.
Summary: This is genuine canon, made in Japan. Although it's appears to be only a piece of plastic, it is very essential if you are serious about photography under bright sunlight. Look at strengths above, there is no reason not to have one. I have a Hoya multi coated filter on my lens and this hood still fits perfectly. I love the dual protection. You already spend about a grand on your lens, don't be cheap on the lens hood.
Pros: Excellent Quality Made In Japan Great protection for the front element Improved contrast in bright sunlight
Summary: Could have gone for a knock-off, but at the end of the day when using a circa $1,000 lens why try to save a few bucks and take a risk? Fitted the 17-55mm f2.8 with a resounding, soft and satisfying "clunk".