A lot of socks claim to be aero, but the Quick-Step Fast Feet 3 Socks are, saving two watts at 50km/h, as demonstrated using a jig that replicates the movement of the lower leg, plus actual riders to verify the results.
Now with an updated cuff, for more comfort and added aero gains, these team-branded socks are made for speed when it's too warm or not convenient to wear the Fast Feet 2 TT Shoe Covers, but you still want an edge over the competition.