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Sure, there are plenty of synthetic baselayers out there, but only the Arc'teryx Men's Phase SL Bottom uses fabric that controls moisture, truly transports moisture away from your skin, and flexes like none other. Slide into this bottom in order to layer up for cold-weather trail running, alpine climbing missions, and day-long ski touring missions into the backcountry.

  • Next-to-skin fit keeps this bottom as close to your skin as possible in order to aid moisture transport and help you stay warm
  • Gusseted crotch offers a supremely comfortable fit where it matters most, and the wide, laminated waistband has a soft finish on the side closest to your skin
  • Phasic SL fabric is hydrophobic in order to help transport moisture away from your skin
  • Phasic SL fabric uses a construction called mechanical stretch that relies on the weave of the fabric to flex, rather than elastic threads, which creates a stronger fabric with more dynamic flexibility
  • Phasic SL fabric incorporates polypropylene yarn with silver ion encapsulated into the fibers in order to provide odor control that lasts longer than chemical coatings
  • Phasic SL fabric is lightweight and has a smooth outer face that allows other layers to slide easily over its surface
  • Flatlocked seams and no side seams make for a comfortable fit, free of hot spots or irritating bulges

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Here's what others have to say...


Does not appear to hold up.

  • Gender:Male
  • Familiarity:I've used it several times
  • Fit:True to size
  • Height: 5'10"
    Weight: 190 lbs
    Size Purchased: Medium

I purchased this product recently and have worn it about 7 times for running, cross fit and pilates. It has only been hand washed. It has started to sag, especially at the knees, and some of the stitching at the ankle has broken loose. I have many arcteryx products, unless I am doing something wrong, I cannot recommend this product. As of July 13, it has developed runs making it useless.


Super Light Super Warm

  • Familiarity:I've put it through the wringer

The bottoms are only 3.5 oz but they keep you so very warm during the bitter cold months. I have worn these boarding and biking. The Phasic SL fabric also does an amazing job of whicking away sweat. These do really well for those nights where you are feeling brave and decide to make the trek to the bar on foot.


Great base layer!!

  • Familiarity:I've used it several times
  • Fit:True to size

Keeps you warm while still extremely breathable. Fit is great, can't even hardly tell you have them on. Going in my flight bag.


These are light and compact

  • Familiarity:I've used it several times
  • Fit:True to size

They will make it into my standard bike-touring kit when travelling outside of high-summer.