Q: Do these replace the whole mirror or just cap over it?

They cap over the factory mirror housing rather than replacing the mirror assembly, wrapping edge to edge to conceal the original paint. Because the underlying mechanism is untouched, everything the stock mirror does still works. Power adjustment and auto-folding behave as before, and the heating element and blind-spot camera are unaffected. The result is an all-over carbon fiber mirror appearance with none of the electrical changes a full housing swap would involve.