I love Swiftwick customer service! Fast turnaround on orders. They make customer satisfaction a top priorty. I've been experimenting with various socks to address tendancy of getting blood blisters under some of my toenails. I have flat feet, bunions, and overpronate so I buy a stability shoe and order half a size up. The FLITE XT 5 med. cushion socks have become my favorite running sock this spring. They keep my feet from moving forward when running down hill. I like the cushioning--not too thick. The arch support feels great and the socks don't "fall down" or slip into my shoe. I've worn these socks with two different brands of running shoes on runs between 4 and 5 1/2 miles. So far no blisters or hot spots.