Macpac Nitro initial impressions and size guide

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  • #3711506
    BPL Member


    So I got my Macpac Nitro in the mail yesterday after about 3 weeks. Thanks @Idownman for the hook up from down under. Easy guy to deal with if anyone is considering a Nitro.

    As I havent had it long enough to comment on its back country performance, I’ll mostly talk about the sizing as I could not find any good info on this. I’ll add details about performance once I’ve tested it for a couple weeks.

    I’m 6’1, 185lbs, 40″ chest circumference under armpits with a mostly-full breath, Athletic build, no fat to speak of on the belly, arms, or back. I wear a 33″ waist pant x 32″ inseam typically. 75″ wing span finger tip to finger tip.

    I normally wear a Medium in base layers from Icebreaker, Smart Wool, and most american-cut brands. Sometimes I’m a large if the sleeves are short or chest is small. I typically size up to Large in my Montbell and MH puffies because I dont like a tight back when my arms are outstreched, but im probably more fitted to a Medium if they would just add 2″ to the upper chest circumference.

    I followed the standard (i.e. only) advice of “size up” and got the Nitro in Large. The Large fits me like a skin tight base layer, along the lines of my Icebreaker Oasis medium, possibly a tad tighter. Its not compression-shirt-tight, but its noticeably tight, particularly under the arm pits (Kiwi’s must have small arms…???). I think the fabric will loosen up over time because the weave is so loose, or at least I hope it does. Its also small in the arms, but not too tight, and I have fairly large forearms where it is most noticeable.

    I did want a nearly skin tight fit, as this will be my active base layer and if this garment is not skin tight it will immediately be a lot less warm than a skin tight version. The Alpha Direct weave is so open that any air movement flows right through it. If there is open space on the back side, air will go right through creating a cooling breeze even at walking pace.

    The sleeves are quite long so its not a problem to use the thumb hook to cover your hands for some slight hand warming.

    Im tempted to size up to an XL, but think I’ll wear the Large for a while and see if it streches just a tad. I think my ideal size is Large-and-a-Half. As usual, I’m cursed with being between sizes.

    If you are similar size to me, but have any fat on your belly, arms, or back, you probably want XL. If you have any fat or have large muscles around your arm pits, an XL is probably wise. If you dont want a skin tight fit, an XL is needed.

    The neck is very small. It may need to be cut for some people. My head barely fits through.

    The Pocket is indeed horrible. Serves no purpose whatsoever. Just a place to put their logo and I hear its rather hard to remove (per other threads). Too small to hold anything but a couple credit cards or Ipod mini (anyone remember those?)

    I also wore it around with my Fauxdini wind breaker. It immediately made the shirt twice as warm. I was very comfortable walking around in the morning mid-50’s watering my yard. This combo is why I bought the shirt, and with the wind breaker I think this will be a dynamite setup for 35-55* dry hikes. I can hike in a thin poly shirt down to the low 50’s, so the Nitro or Nitro + Fauxdidni should get me down near freezing as long as im hiking 2.5-3mph.

    Last thought, the Direct fabric catches EVERYTHING. Your fingers, wood, duff, seeds, things you didnt even know were catchy, this will catch. I dont think this garment can be worn alone where I live (SoCal). With all the spikey crap in the back country, it would immediately snag, or worse, pokey thorns, sticks, and seeds like foxtail grass could easily become embedded in the weave and would then have to be tediously picked out individually with a tweezers as to not destroy the weave or pull the fleece puffs out of the weave.

    Its so catchy, it sticks to my shaved head! I shave my head to 1-2mm so its slightly stubbly/rough.  When I pull the hood on, i have to lift it over my head so it doesnt touch until its in-place, then let it down. Then my hair is spikey enough the hood will literally stick to my head like I glued it on, anywhere in my range of motion. It absolutely will not slide over my head. I’d rip the weave before it slid on like a normal nylon/poly/tafetta hood. I’ve never experienced this before with any hat or hood, and I wear hats a lot. I guess my other fleeces do this to a much lesser degree, but its very noticeable with the Alpha Direct

    Overall im happy with the service from Idownman and really like the shirt in spite of its quirks. I definitely see it filling a hole in my setup.

    for about 8oz I can have the Nitro + Fauxdini compared to about 14oz for an Arcteryx Konseal + Fauxdini, and I expect the Nitro to perform better wicking/venting

    This would be a perfect piece if they would just remove the pocket, open up the arm pits quite a bit, open up the neck just a tad, and possibly shorten the sleeves 1″.

    Bill in Roswell
    BPL Member


    Locale: Roswell, GA, USA

    Marcus, thanks for posting the thorough review. I got a Nitro from iDownman last year. I’m 5-7, about 42-43 chest. The XL fits me like the L fits you. In other words it fits like Arc Teryx made it. Boxier Patagonia fits my old body better. I do love the performance of Alpha. I sweat greatly regardless of temps. I’m in north GA, where it’s always humid but never cold for long. The Nitro with Smartwool 150 wt. base layer is super for working hard on the climbs (this isn’t crazy New England climbs, but quite steep and relentless in number). My old Marmot windbreaker makes a very versatile system for this part of the country. I do keep a puffy or vest handy for stops. Still, for 6 ounces you can’t beat the versatility. I’ll get another Alpha hoody, but from Senchi via Instagram, or Timmermade which only does full custom for about the same money as Macpac.

    Adam Kilpatrick
    BPL Member


    Locale: South Australia

    Friends have the Nitro and I’ve tried them on in store. They are on sale pretty regularly as are many things at Macpac these days.

    Really unless you spend most of your time on very groomed trails I wouldn’t trust it much. A vest version would be much more versatile, and durable I think for most people. The sleeves cop most of the abuse/harder to keep away from danger (like a twig….). Ive thought about getting Senchi or someone else to make one for me, but its probably not worth the effort given the trips I do. I’d probably be better off with a MYOG wind vest made of something like membrane from RBTR.

    BPL Member


    I took this on another short evening hike/jog last night up one of the local mountain fire roads.

    It started out about 74* with the sun just setting and I finished around 65* in the dusk. No wind at all.

    This time I wore the Nitro as my only layer and WOW I am really impressed with it as a solo shirt. Its much, much more comfortable as I now realize the armpit pinching was actually my Icebreaker 120 bunching up underneath it (and the icebreaker fits me well by itself, its just the Nitro is very trim fitting, which I actually LOVE when its not layered).

    Basically I discovered I love the cut for a solo layer, but the cut is much less comfortable if you have anything under it besides a compression shirt. The Nitro has a true athletic cut (not an ‘american athletic cut’ which isnt form fitting IME). Its slimer in the waist and belly than current Arcteryx. I wish I could find more regular shirts cut like this! Everything american is baggy in the waist and belly.

    Without a base layer the small neck did not bother me

    I started out with a light jog up a low grade as I wanted to test its performance in warm weather with medium-high output. At jogging pace I think it was actually cooler than my usual ultra thin poly long sleeve shirts because any wind just goes right through the Nitro. It close to not wearing a shirt. I only sweat a tad and it evaporated quickly.

    On the way down my dog was tired so we just slow walked. Temp fell to around 65, slightly damp air moved in. When slow walking, it was nice and warm. In my poly shirt I may have been a tad cool, but the Nitro was very comfortable.

    So I’m revising my initial thoughts a tad. They almost need to offer 2 cuts – a Base Layer cut (the existing product) and a Layering Cut, which would just be cut a tad looser in the armpits and neck to allow for a base layer.

    The Alpha Direct is very soft and nice directly against the skin.

    I think this could actually stand up as a moderate-hot weather shirt if it was white/off white, into the 80’s, because it breathes so well.

    Also after reading the recent article on Fleece performance, the summary seems to be that loft directly correlates to warmth, and weight has almost no correlation. Comparing the Nitro loft to other fleeces like a Arcteryx Delta (forget the modifier) or Konseal microgrid the Nitro has considerably more loft. I guess this is how they get so much warmth out of such a light garment!

    Im totally sold on Alpha Direct and will be looking to pick up other AD hoodies like the Senchi or a custom shirt that accommodates base layers slightly better. Its by far the best active garment I’ve tried to date.

    Sean P
    BPL Member


    Locale: S.E. Australia


    I have both the Nitro and another macpac garment, the Pisa, which is basically alpha direct with a pertex quantum air shell sewn over it.

    It’s never cold enough in SE Australia to wear the nitro as a running top but in freezing weather the Pisa is something I put on straight after a run – i take of my running shirt, don the pisa  and sweat through it until I’ve cooled down.  I never get chilled with this jacket – sweat just seems to evaporate through it – and I am a heavy sweater.

    The Nitro itself is active insulation par excellence for humid alpine Australian conditions of around freezing.   Also works very well as a sleeping base layer under a quilt.  A versatile top for sure.

    BPL Member


    I also have a large, but I am smaller than Marcus – 5’8″, 175ish. The large is slightly looser than I would prefer. I have always worn it over a base layer. I suspect a medium might be too small for my purposes, but if you want a “Base Layer cut” as Marcus says, you might try that size.

    I shave my head, too, but haven’t had the Sticky Hood issue Marcus has.

    I agree with Marcus’s thoughts on the temperature range. Nitro + windshirt (in my case, a Montbell Tachyon) is a great and versatile combo. For less weight than my R1, I get a lot more options to tackle a range of temps and conditions.

    I agree that the Nitro seems like it could be fragile. But I’m afraid to test that, so I don’t know if it’s actually fragile or not.

    EDIT TO ADD: Contrary to speculation I’ve seen elsewhere, Nitro + windshirt is not a puffy replacement. While the combo is warm, my puffy is warmer, particularly when sitting still in camp.

    BPL Member


    I recently got a Superior Fleece Brule in 90 wt Alpha. I’ve only worn it once, in 50F – conditions too warm for it. But I wanted to see how it would handle moisture, and so wore it next to skin under a windshirt for 1.5 hours at about 4.5 METs. Got very sweaty, which I expected. The windshirt was very damp throughout, but the Alpha was bone dry apart from the pits, which were merely moist. I was actually fairly comfortable despite all the sweating during this period, probably due to all the evaporative cooling going on at skin level, as I was not wearing a wicking baselayer.

    I then took off the windshirt and wore the Alpha next to skin as the temps climbed near 60F for another 4 hours of hiking at same pace. Wind started picking up near the end and donned and doffed the windshirt a couple times, as needed. I was very comfortable during this period. 60F is obviously way too warm for 90 wt Alpha, but as mentioned above, the knit is wide open to a walking breeze.

    I think Alpha works well next to skin when it’s warm out, as the evapoative cooling at the skin is very effective due to Alpha’s being a sieve. But I think next to skin probably will not work as well when it’s cold out, which is when I would actually wear Alpha in earnest. Then, Alpha’s lack of wicking action and tendency to leave perspiration on the skin would work against the wearer.

    On the other hand, maybe it would work a bit like a mesh baselayer in winter – quite well. The inner surface of the Alpha 90 (which might be the same as Macpac’s) is a little bit furry, like a mangy, short-haired beast, and so may function a little like a mesh shirt (e.g. Brynje).

    I plan to wear it next to skin as a sleeping shirt on a trip starting this week. At 5 ounces, it is just barely heavier than my lightest merino sleeping T, but it has a warm hood and is very cozy next to skin:) It will also be available to wear under a rainshell and I’ll probably wear it next to skin for that too, as the temps are likely to be 40-50F and a little evaporative cooling at skin level will probably be OK.

    This is my first Alpha garment and I’m probably overly optimistic. We’ll see how I feel when stuff starts getting stuck in it.

    Victor Jorgensen
    BPL Member


    Locale: Northern California

    I got my MacPac Nitro yesterday.  I am usually a medium and went with the Large after reading this thread, and having a discussion with idownman.  He is still helping people in the US get this elusive mid-layer, and was a pleasure to do business with.  Mine is the “Medieval” color, a dark blue.  The photo on the macpac website depicts the color accurately on my computer screen, and I am really happy with it.

    Delivery was almost one month, so I had to plan ahead.  Weight was 5.5 ounces for the large, on my scale.

    To me, the fit is like a medium with a couple extra inches in torso length, and generous length in the arms.  The hood has no adjustment, but fits my head and neck better than many other hoodies (like Kuiu), because there is adequate neck length sewn into the hood.


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