Swiftwick Sock Sizes
Sock Size	US Men's Shoe Size	US Women's Shoe Size
S	N/A	5-7.5
M	6-9.5	8-10.5
L	10-12.5	11-13
XL	13-15	N/A

Sock Geek Says:

Swiftwick running socks are knitted at 200 needles, the highest density you'll find in any running sock on the market today.  The benefits of this high needle count include:  keeps foreign material (ie. rocks, road debris) from penetrating the sock, creates a second-skin feel, prevents shifting or bunching, eliminates the risk of friction blisters, and makes your shoe fit more comfortably.  Also, you get a softer, denser, and more durable sock.  Extra compression (21.1 mmHG) promotes blood flow to your feet which increases your performance by reducing foot and leg fatigue.  Heavy use of the high performance fiber, Olefin, which moves moisture like a champ and has a very low friction coefficient.

Try a pair, you'll be hooked!

Swiftwick Performance Run Sock Specs

Sock Fibers: