Arc’teryx Phase SL Base Layer System

Winter has to be my favourite season, despite how difficult it is to dress for. The love-hate relationship with managing your body heat is one that can really discourage play outside during the winter if you haven’t fine-tuned it. Too cold is miserable, but too warm will mean sweating which will undoubtedly make you even colder! It took me almost two seasons of ice climbing to figure out the best system for me. The key to my success outside while climbing in the cold is to not sweat on approaches. The best way to combat the sweat is a wicking base layer system. After an ‘unplanned’ (ya right….) visit to the Arc’teryx outlet store in Vancouver last summer, I found the Arc’teryx Phase SL Base Layer system and haven’t looked back. I started out with two camisoles and a long sleeved crew neck, I now own four pairs of the underwear, one bra, two camisoles, a long sleeved crew and a long sleeved zip up.

With a degree in textiles, I’m pretty picky with how the fabric feels, how it’s put together and most importantly how it fits. This means for me, it starts in the fitting room! My base layer is the first thing I put on. If it’s not comfortable or fits properly, you’ll feel it, be stuck wearing it all day and end up wondering why you’re uncomfortable and grumpy. Luckily, the experience in the fitting room was great. I am a pretty close to a standard size medium in tops from Arc’teryx. The cami’s fit well considering I have a bit of a longer torso/back. The length is long enough to be tucked into a pair of pants or sit under a harness and the neckline sits high enough that I don’t feel like I would be exposing too much if I were to lean over. The straps don’t dig into my shoulders and the shape through the body is form fitting and follows what curves I have without being tight. As for the long sleeved crew neck, the fit was also spot on. With broad shoulders across my back, how long sleeved shirts fit tend to be the selling point for me. I’ve tried on countless shirts where once I put my arms in front of me, my back looks like the hulk trying to rip out of a shirt. The back of the crew neck in combination with the sleeve length is perfect. The sleeves just cover my wrist and the back and body is long enough to accommodate moving my arms above my head and across my front without the shirt shifting or exposing my stomach. I did find the size of the neck hole a bit snug to get on, but it does stretch, and once it’s on, it fits great. (I wouldn’t recommend trying to put it on or take it off with a helmet on).


By far the best part of the impression in the fitting room was how easy it is to move in them! For a fabric that does not contain any lycra or spandex type fibres, they are surprisingly comfortable. The fabric is super lightweight and smooth feeling as well.

After falling in love with my first three pieces, I expanded my set to have underwear (trying the boxers, brief and bra), and a long sleeved zip. According to my measurements, I should be a size large for the underwear. They do fit, but seem too loose and tend to move around under my pants when wearing them. So I opted to go a size down with a medium. The boxers are great. They do a good job of covering my ‘gymnastics bum’, and the waistband still sits where it should. The coverage from the briefs is still good and the waistband sits well under all of my shell pants. Both styles fit and cover well, so after sweaty approaches, I don’t feel exposed when its time to change my base layers. The bra fits well and is made of the same thin lightweight fabric. It doesn’t provide a ton of support or compression, but the light fabric makes it feel like you’re not wearing one. The only downside is that the thin fabric leaves nothing to the imagination in terms of covering nipples. The ¼ zip has the same fit as the crew neck, having nice long sleeves and a form fitting shape through the body. The zip makes it easier to take on and off and allows for me to vent without removing a layer.


The fabric for all of these pieces feels incredible. It’s easily the best part of all of these pieces. It’s a super lightweight polyester blend with UPF properties as well as amazing wicking ability. Furthermore, these pieces don’t absorb sweat… at all! They do such a great job of wicking that you get that cool feeling while you’re still going… so they keep you dry and don’t smell the next day.

Despite their intended use as a base layer for high intensity, sweaty pursuits, I’ve used all of the pieces for a variety of activities. The cami’s are great for runs and hikes on hot days, indoor and outdoor climbing sessions and paired under other layers on cooler days. I’ve worn them multiple days in a row on road trips. Even with sweating, they don’t smell! I’ve used my long sleeved crew for a full season of ice climbing as my ‘hike in’ shirt to keep me cool and sweat free on steep approaches. I have also worn it to bed to add some warmth but keep me from sweating in my sleeping bag while camping in the mountains. In the warmer months, I’ve also used both of the long sleeved shirts to protect my skin from the sun without adding any insulation. The long sleeved zip quickly became my go to layer in shoulder season for hiking into crags and on cooler climbing days to keep me dry and keep the wind off of my skin. I also like to use it for runs on cooler days. It will replace my crew neck as my approach layer for ice climbing since the zip allows for me to vent my chest once my body heats up. All of the underwear pieces feel amazing and on high activity days are my staples to keep me comfortable when sweating.

With proper care, all of the pieces I have are still in great shape even with such a thin fabric. I do wash them in cold water and hang to dry (unless I’m pressed for time) and the only visible wear is the printed tag on the inside has begun to wear out. The thin fabric used in this base layer system means I can pack a number of the pieces in my bag on camping trips (taking up so little space), and they still look good after being compressed into a stuff sack.

I do have two things I would love to see in this base layer system. The first is having the bra have either thicker fabric in the front or some sort of layer to *ahem* do a better job of hiding when you’re cold. The other being that I would love for Arc’teryx to come out with a base layer pants or tights to be made out of the same light weight fabric.


In summary, Arc’teryx have done a great job of mastering the fit, function, durability and versatility of the pieces in the Phase SL (superlight) base layer system. I do realize the price point is a bit higher; however, feel that to be comfortable in outdoor pursuits, you need good quality pieces. Think of it as an investment in your comfort outside.




3 thoughts on “Arc’teryx Phase SL Base Layer System

  1. Lawrence Crowley says:

    Great review Lindsay.
    The last shot is my favourite… Not sure why but I’ll sure be paying more attention to your reviews from here on in.


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