Originally Posted by cyccommute

There are many versions of this kind of fender. They aren't meant to act as anything other than a guard to keep stuff from flying up under your chin in sloppy conditions. They are aimed, primarily, at the mountain bike market because full fenders don't work for off-road riding.

That said, nothing that attaches to the bike will keep your feet dry in rain. The rain that falls is going to make your feet wet so you should have other methods of keeping your feet dry like shoe covers or waterproof shoes.