SmartWool PhD Running Ultra Light Mini Socks

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Manufacturer Description

Our ultra light cushioned PhD Running Ultra Light Mini is the perfect running sock for mild weather and shorter distances. Thanks to WOW technology in high density impact zones, shock and abrasion are reduced.


  • Knit in USA
  • Fabric – 66% Merino Wool, 31% Nylon, 3% Elastic

    Elastic on the Inside Upper
  • 4-Degree Fit System for all-day performance fit
  • WOW technology in high density impact zones to reduce shock and abrasion
  • Merino wool inside for moisture, temperature and odor control
  • Double ribbed cuff for secure fit
  • Strategic mesh zones for maximum ventilation
  • Measured size medium
    • Weight – 20 g (0.7 oz) per sock
  • Retail – $15

YMMV Review

Socks are an item most people take for granted. Not a whole lot of thought is put into what socks you are going to wear. I know I was that way. Then I wore some good socks and realized what I was missing. The right socks can make a big difference in overall comfort as well as performance. With the SmartWool PhD Running Ultra Light Mini Socks I have been happy to have a sock I could just grab and go with and not have to think about them. I know they will work. If you would like to learn more about wool, check out the link below.

Design ★★★★☆

The SmartWool PhD Running Ultra Light Mini Socks are made out of a blend of merino wool, nylon, and elastic. This blend is optimized to give the benefits of each fiber. Merino wool is used on the inside for moisture management properties, temperature regulation, and odor control. Nylon increases the durability of the sock and is used on the outside. Elastic is used in strategic places to improve the fit of the sock. SmartWool uses a 4 Degree Fit System in their PhD socks. It is a proprietary four-point sport supportive system that provides a secure, comfortable fit around the heel, arch, and instep. The four locations include the ankle band, upper instep band, lower instep band, and arch band. There are also mesh zones for breathability on the upper foot, four of them to be exact.

Side View

The socks are built using SmartWool’s WOW technology. This technology is used in order to get as much wool next to your skin as possible. The WOW (Wool-on-Wool) technology replaces some of the nylon in the high impact zones with more wool. These zones are located in the heel and forefoot. One thing I am surprised that SmartWool has not done is make left and right foot specific socks. With all the technology they employ that seems to be the next logical direction. Smartwool makes their socks in sizes based on shoe size.

Fit ★★★½☆

The SmartWool PhD Running Ultra Light Mini Socks fit me well. I am right at the edge of the sizing chart being a men’s size 9. A size 9 normally corresponds to a large but I like the fit better of the medium which covers up to an 8.5. If you are on the edge I would size down for a more precise fit. With the elastic in the socks they contour the foot well. My wife has also tested the pair as she is a medium and she has had no issues as well. The socks stay in place when running or just wearing around. By not moving around it is harder for blisters to form. The sock comes up just above my ankle bone. A good length for trail running. They make a shorter version that I like better for road running.

View of them on

Performance ★★★★☆

Even though the socks are the ultra light model, they still tend to be slightly warmer that the thinnest synthetic socks. The socks do a good job managing moisture. My feet have not felt hot and sweaty, just a bit warm. The ultra light model has a little less cushioning than the light version. I like the light version in the winter as they are a bit warmer. The best thing I can say about socks is that you do not have to think about them and that is the case with these. They just perform as expected.

Overall ★★★★☆

I have been impressed with the SmartWool PhD Running Ultra Light Mini Socks. They fit well and perform as you want them to. They can be a little on the warm side on the hot summer days here in Bend but they manage the moisture well. I have worn these socks for runs up to 40 miles and had remarkably no blisters. Some of that is also due to wearing the correct shoes. SmartWool is really good at making socks and it show with these. The durability has been good and I have had no issues with any of my SmartWool socks. With many options, thicknesses, and heights there are options for everyone. They even are good for other activities other than running. They are on the expensive side at $15 but you get what you pay for. As always, Your Mileage May Vary.


  • Great fit
  • Good moisture management
  • Durable


  • A bit warm on the hottest days
  • Price


About the Author

I am an avid runner, cyclist, swimmer, hiker, climber, skier and many other activities that would make this list too long. I started Your Mileage May Vary Reviews in Early 2011 to combine two of my passions: sports and gear.

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