Performance fabrics generally fall into two major types: polyester and merino wool. Both will wick moisture, dry quickly, regulate temperature, and feel comfortable all day, plus control the growth of odor-causing bacteria, whether due to fabric treatments or natural properties. Both are great choices, with a few minor differences.
Polyester is the performance fabric most people are familiar with; it wicks, dries, and keeps you comfortable. It cannot, however, absorb moisture; it merely transports it away from the skin to dry quickly. This means it works great with shoes that have adequate ventilation, by which moisture can easily escape, as is the case with the majority of Vibram Five Fingers. Toe socks featuring polyester fibers such as Coolmax are a ubiquitous staple beloved by runners worldwide.
The alternative is merino wool, an all-natural performance fabric that has similar moisture management and temperature regulating properties as polyester, but feels less clammy when worn directly against the skin. Merino wool can absorb a significant amount of moisture before feeling damp, meaning it can be quite comfortable under less breathable shoes, as it takes longer to become overly saturated. It also insulates better than polyester, so it excels in winter, when you might want more warmth, plus any moisture will be absorbed into the interior of the fiber, where you won't be able to feel the chill. Merino wool dries a little slower than polyester, so on lengthy summer jogs you might get too warm or damp.
Both fabrics are adored for their performance characteristics, and different body types will feel differently about them, but in general merino wool is what you want for colder runs, and polyester when it's sweltering. For serious runners, however, you'll do best with one of each, to compare side by side.
So, what are the best socks for Vibram Five Fingers or other high-intensity pursuits? Seem below for some of the best out there.