Been using the Black Keo cleats for a few months and managed to break one the other day, my LBS don't carry them, so I had a Red pair that were new in the box that came with my pedals, slapped them on my bike shoes and man did it bother my legs, it really was causing some cramping in my left calve and my glutes. PS I put them in the same spot and angle as the black ones due to the wear signs on the shoe.
Now every one says the black are hard on the knee's I guess I was used to them, I may have to order another set on line.
Does anyone use the black and prefer them to red. :