AFAIK (from personal experience) when Look pedals first came out there was a single, black cleat available known as "delta". Then a few years later they came out with a new cleat (for the same pedal) that was red and known as "ARC" or "delta ARC". The idea was to give some rotation. You can use either one (based on preference).

Later, Look came out with Keo pedals, and the cleat looks much the same but if you look closely they are not. The Keos are narrower in the rear which is the most obvious to me. The Keos come in 3 colors, the difference being the "grey" is half the float of the original delta ARC or Keo red.

scott s.
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