Mountain Core Smock



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Combining revolutionary PrimaLoft® Active insulation with our own lightweight and wind-resistant Flexile shell, the Mountain Core Smock is an incredibly effective insulating layer that still provides excellent breathability during activities with variable output. The large through-pocket is the perfect handwarmer for before and after your early morning run.
PrimaLoft® Active is built from a synthetic plume woven through a knitted mesh, offering the warmth of a fleece but with less than half the weight. With all the benefits of synthetic insulation, Core products work wet or dry with incredible wicking properties to ensure you won’t stay wet for long. Using the 125g/m2 weight of PrimaLoft® Active means 65% of the insulation is derived from recycled sources.
The stretch nylon Flexile shell fabric has a high degree of wind and water resistance whilst retaining good breathability, perfect for mixed conditions.
Pair with a shell in bad weather to increase the insulating benefits and protection.

PrimaLoft® ACTIVE Insulating Fabric weaves PrimaLoft® fibres onto a mesh, giving a super high volume and open structure. Fabrics insulate by trapping pockets of air that the wearer’s heat cannot pass through. Core structure is exceptional at creating these pockets. However the openness also allows for a light breeze to disturb these air pockets and remove the insulation effect.


We always choose synthetic insulation over down to be sure that we can get warm even when everything is wet. We believe PrimaLoft® make the best synthetic insulation and so it is an easy choice for us. 125g/m2 PrimaLoft® ACTIVE uses 64% post-consumer recycled material, it is also bluesign and Oeke-Tex approved.


We can quote all the performance figures we like but what really sets the Mountain Core apart is the sheer cosiness of it. You will fly down those final descents, knowing you get to pull this on at the end of your run. But be warned, it can be very hard to take it off once your snuggled into it!


Stretch Panelling
Wind resistant
Warm when wet
Large front fleece lined through-pocket reverses to form a fleece pillow
Key clip
YKK® quarter-length zip


Flexile: Nylon/Spandex mix
4-way stretch
Quick drying
Fast Wicking
Wind resistant
DWR: Durable Water Repellancy
64% recycled insulation
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What Insulation Do We Use?

 OMM use PrimaLoft® synthetic insulation as it is widely regarded as the best quality available; with insulating properties very close to that of down plus largely manufactured from post-consumer recycled product (PCR). Usually manufactured in a roll or sheet of ‘wadding’, think loft insulation but a lot nicer! From PrimaLoft® we mainly use their Gold Eco with Cross – Core Technology, their highest rated and most sustainable option plus the latest ACTIVE fabric in the Core Ranges, built from a synthetic plume woven through a knitted mesh, CORE offers the warmth of a fleece but with less than half the weight.

How do I care for my Insulation?

Just like owning a top end sports car, a piece of performance Insulation is only as good as how well you care for it. In the same way a sports car still needs oil changes and screen wash, you need to regularly maintain your OMM Clothing to keep it performing at its best. It is important to follow the Product Care Instructions and use the correct wash and/or proofer product as these can affect your clothing’s performance. The benefit of using a synthetic insulation is it is much more resilient when washing plus dries a lot quicker.

How much insulation do I need?

That depends how cold you expect to get or perhaps you know you always run a little hot and so don’t need so much. The amount of insulation a product has, generally the warmer it will be. The amount of insulation in synthetically insulated products is quoted as per square metre. When using PrimaLoft® Gold Eco, the lowest value we use is 40gsm, up to 233gsm in our warmest Mountain Raid Sleeping Bag. We also use PrimaLoft® Active which is a much more breathable option as iti does not require the layers of fabric either side of it to stabilise the insulation. Though not as warm aas traditional options, the breathability and next to skin comfort makes it a great option. 

What's the fit like?

 Most OMM Clothing tends towards the “fitted” end of things. Designed for performance use, the fabrics often work best when dead air is reduced whilst also reducing drag and bulk when moving quickly. We use three different fits in our clothing ranges; Contact Fit, Fitted & Regular Fit. Most of our Insulation uses our Regular Fit, with a little more room and a squarer cut. You’ll find a link to the Fit Guide on each product page. You also find a link to our Size Guide, a more in depth table that shows measurement ranges for each size. Insulation should fit comfortably over a First & Mid Layer and are designed to work well with our Outer Layers. 

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