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Altitude 'Mongrel'

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Gothic Grape

If you’re looking to add a little extra fun to your next adventure, the Women’s Altitude ‘Mongrel’ is for you! Don’t let the name fool you, this is one seriously good thermal Base Layer. The perfect combination of performance, warmth and comfort with a little bit of fun thrown in for good measure.  

Get in quick, all Mongrels are strictly limited edition and once they're gone, they're gone for good.

Flatlock stitching, raglan sleeves and tag free to eliminate chafe and maximize comfort. The drop back hem and extra body length is designed for tucking into your outer layers. Thumb loops keep your hands warm and stop your sleeves riding up when layering. 

Ultra Trail Australia mandatory gear approved thermals

Why you’d buy this: You like your stuff to fit nice and close to your body whether you wear it on its own, or under another layer and don’t want any extra bulk or bunching. You might also want a bit of extra length which this one gives you. It’s super soft and comfy, and 96% merino so it’s super natural which means almost no microplastic issues when you wash it or landfill when you’ve finished with it.

As with all our clothes, the merino delivers natural temperature regulation, breathability, moisture wicking and odour resistance.

Designed to be worn as a body tight ‘contact fit’ layer. Slightly looser than the Altitude long sleeve styles.

Drop back hem and extra length in body. 

Thumb loops. 

Model wears size medium.

Size Guide. Contact Fit.

Snow sports



170gsm lightweight

96% superfine Australian Merino

4% Elastane - for an easy all-way stretch.

A MicroMerino® Fabric.










Customer Reviews

Based on 9 reviews
Dipika Delmenico (Melbourne, AU)
A purely Pedigree mongrel

This is an absolute winner. The look, the feel, the fit, the functionality. The colours are rich and a burst of winter richness.

Judi Moncur (Beechworth, AU)
Love the style but comes up very small

I really like the colours- makes for a much more interesting top than the usual. I found this came up really small compared to other merino outdoor tops I’ve bought- just surprised that no other reviewers have said it was true to size. I’m normally a size 8 , 55kg with narrow torso, so I ordered a size S, my usual size - but I couldn’t even get it on, so exchanged for a size M. IoMerino we’re very helpful and handled the exchange quickly. The size M has just arrived, still a bit tight, but wearable, though I prefer a bit of room in these tops and to allow for shrinking after washing - seems ridiculous to get a Large, but I might have to do that next time. Have some of them been mislabelled? Loses one star for the sizing.

Hi there Judi,

With the sizing of our Mongrel items, they are part of our 'Contact Fit' range, and so are designed to hug very close to the body.

You won't have to worry about sizing up to allow for shrinkage thankfully, as our wool has been superwashed, and so doesn't shrink.

All the best,

Sally (Ballarat, AU)
Mongrel for me

Love the mongrel, love the altitude fit, true to size, comfortable and versatile.
Thanks IO

Sarah D (Melbourne, AU)

I love the brightness of the mongrels, I have a few in my collection. Purples are the best!

Kerry (Albury, AU)
Comfortable and colourful

I bought both Mongrel short sleeve and long sleeve. So far I’ve only had a chance to wear the long-sleeve and I love it. I like that there’s a bit more room in the sleeves so they’re not skin tight, and I didn’t realise there’s a thumb hole which I love (good length for colder days). I would have liked a bit more fabric in the boob area, but otherwise the general fit is good. The mix of colours and stripes is a delight.

Jo P - Adelaide (Adelaide, AU)
Amazing top

I’m so happy with this top! Thankyou io! The fabric is wonderfully soft and the colours are such fun - I have black and grey base layers and feel much brighter and happier in this! The size chart is spot on. Since receiving this I’ve ordered more from io, really like their philosophy and products are amazing.
Traveling to Alaska in May, and the UK next year. I’m carefully building a small travel wardrobe (which I’ve already started to wear ALL the time - these clothes are so so comfy!) I am even more thankful to have found a local company to support.