Up to now I've been using Thorlo and Fox River boot socks. I have about 8 pairs and was planning to purchase another 8 to 12 before my deployment. I've found that with socks, like ammo, you can never have too many. I decided to give Covert Threads a try.
I ordered from their website (Clicky), and received all of the socks within a week. I specified I was a Marine and got three pairs for free on top of the ten pairs I purchased. Total with shipping was a bit shy of $100.
So far I have been very pleased with these socks. They aren't as high as the Thorlos or Fox River, which is good considering they always bunch up at the top of my boots whenever I move a lot. So far no blisters or hot spots, but then again I haven't had a blister since before boot camp, almost two years ago. They have X-Static fibers for odor control. So far odor has been a lot less than with other socks I've used, or non-existent in some cases.
They have several other types of socks as well, including PTs. The Sand ones I have are for hot weather. They even have their own fire-resistant T-Shirts, but Medium is constanly sold out. They do have Large and X-Large in stock though.