Model Number:

Thin and lightweight, Smartwool Men's PhD Running Ultra Light Micro Socks feature Smartwool's unique pairing of merino wool with synthetic fibers in a snug, performance fit. Merino wool naturally wicks moisture to fight blisters and resists odor build-up. The Ultra Light thickness features no added cushion underneath, yet is durable and protective thanks to high-density fibers at the heel and forefoot.


  • Medium-thin sock with no added cushion underfoot
  • 4Degree Elite Fit System combines 2 elastic types paired with wool for greater stretch that improves performance fit
  • ReliaWool Technology at High Density Impact Zones reduces shock and abrasions with increased durability
  • Mesh zones for ventilation and comfort
  • SmartWool inside for natural moisture, temperature and odor control
  • 1.5" tall low-cut


  • 57% Merino Wool / 40% Nylon / 3% Elastic

Sock Performance Characteristics

Sock Thickness What's this?

  • Extra Thin
  • Thin
  • Medium
  • Thick
  • Extra Thick

Sock Height What's this?

  • No Show
  • Low
  • Quarter
  • Crew
  • Knee High

Customer Reviews

Comments: Smartwool is amazing! Great products that are worth the price. These are thin, like a second skin, & breathe better than any synthetic fiber only socks I've ever worn. You'll love them.
From: Aaron, Lincoln, NE, USA. October 6th 2014

Comments: I purchased these because I have a pair of trail shoes that I really like, but they didn't breath very well. I have worn the SmartWool Light for years now, and they are the only socks I run in. But, my feet were getting extremely sweaty. These worked out great for allowing my feet to breath a little bit more but still get the comfort of a SmartWool sock.
From: Russell, NM, USA. July 4th 2014