I have some 646's and some 545's. The clamp portion of the pedal turns independently of the outer platform, so when you clip it, it's easier to find the cleat.
When you ride with regular "non-cycling" shoes, you can feel the inner part, but you quickly get used to it.
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
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