From Ron's Bikes:
Woolie Boolie socks made in the USA by Defeet::
I get about a week out of them in the winter between washes. nice sock, some say the nicest. we will also say the nicest for obvious marketing reasons.
discription of sock by defeet:
"A DeFeet favorite, the Woolie Boolie is padded throughout the footbed and on the cuff, keeping you warm in any season without getting too hot in mild weather. This sock is available with either USA Merino wool or a blend of Merino and Repreve®, a recycled performance fiber locally manufactured from recycled plastic bottles, reducing landfill waste.
Wool has naturally antibacterial properties, so it takes a lot of sweaty abuse to make a Woolie Boolie stink. Wool also pulls moisture away from the body, keeping feet warm and dry in all kinds of weather.
As a thicker sock, the Woolie Boolie has a mid-density padded fit profile for the rigors of mountain biking and endurance for hiking. Thickest DeFeet sock; less compression than the Wooleator."