Mid Layer

Core Tee



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The Core Tee takes the lightest 75g/m2 weight version of PrimaLoft® ACTIVE, as used in the Core Vest & Hoodie, to create an incredibly warm yet light layer, either as a standalone or as part of a cold-weather layering system.

The Core can be worn next to the skin or else pulled on over a first layer as added insulation but at just 87g and with a tiny pack size, it can be carried without weight penalty when not needed.

PrimaLoft® ACTIVE has incredible air-permeability, meaning when worn alone, excess heat is easily shed, stripped away by any air movement but once covered with a shell or windproof, that heat is trapped close to the skin. This allows for easy control of temperature during varied output or changeable conditions.

PrimaLoft® ACTIVE blurs the line between wadding insulation and fabric; PrimaLoft® ACTIVE loosely weaves PrimaLoft®’s industry-leading insulating fibres through a fine polyester mesh. The resultant structure is warmer and less than half the weight of a conventional fleece product – Down like performance when dry whilst also still performing when wet.


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. Core uses this to its advantage; put a light shell on over the top for the best possible warmth to weight layer and then when you get too hot adjust/remove only the shell and you can keep pushing hard to the summit without a bulky layer to stash.


A single mesh fabric holds the insulation plume in place reducing the need for extra fabric layers and halving the weight and pack size.


At OMM we always choose synthetic insulation over down to be sure that we can get warm even when everything is wet. PrimaLoft® make the best synthetic insulation. PrimaLoft® ACTIVE Insulating Fabric Technology uses 58% post-consumer recycled material it is Bluesign and Oeke-Tex approved.


Continues to insulate even if wet
Flatlock seams positioned away from shoulders
58% Recycled Fabric
Soft rolled collar
Reflective logo


Colours: Dark Red, Black, Blue
Fabric: PrimaLoft® ACTIVE 75g/m2
Weight: 765g
Sizes: XS / S / M / L / XL

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Is a First Layer the same as a Baselayer?

Yes & no. We don’t use the word baselayer as this is more accurately used to describe tighter fitting ‘skins’ or compression garments. Our First Layer pieces are designed to be the start of your layering but you may decide to wear a tighter ‘baselayer’ underneath. Our First Layers work best next to the skin and use fabrics designed to wick sweat and dry quickly whilst feeling soft against the skin and minimising rub points. 

What's the fit like?

 As discussed above, our First Layers are different to Baselayers in that we do not make them skin tight. Most of our First Layers use our Contact Fit (you can find an exact Size Guide on each product page, plus a guide to our Fit), the fabrics work best close to the skin but do not need to be ‘sprayed on’. 

Can I wear these under a pack of vest?

 Yes! All our products are designed to be used in conjunction with packs and vests, though of course the lighter weight products may not last as long as a heavier weight equivalent. We have moved seams  away from areas likely to rub such as the shoulders and use flatlock stitches to reduce bulk and friction. Bobbling of the fabric is a normal part of wear and tear and will not effect 

How can I stop my First Layer smelling?

Wash it! You can find a full Product Care Guide here and at the bottom of the page. A number of our First Layers use Polygeine which is a long lasting treatment to the fibres that inhibits bacterial action. You can also use specific wash products designed for use on sports gear, that kills off bacteria without damaging or astringent detergents and high heats.

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What's the fit like?

Most OMM Clothing tends towards the “fitted” end of things. Designed for performance use, the fabrics often work best close to the skin whilst also reducing drag and bulk when moving quickly. We use three different fits in our clothing ranges; Contact Fit, Fitted & Regular Fit. This gives you an idea of how the Midlayer is meant to look and fit. 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. Midlayers should fit comfortably over a First Layer and are designed to work well with our Outer Layers.

What is Core?

 A new concept in active insulation; the OMM CORE Range is made entirely from PRIMALOFT ACTIVE ultra-light insulating fabric.
Built from a synthetic plume woven through a knitted mesh, CORE offers the warmth of a fleece but with less than half the weight.
Paired with a shell, the CORE is an incredibly effective insulator but thanks to near-total air permeability, the lightest breeze can take away that heat. This allows you to keep your CORE layer on even when you have warmed up and you can thermoregulate by removing/unzipping your shell.
CORE works wet or dry with incredible wicking properties to ensure you won’t stay wet for long.

How do I care for my OMM Midlayer?

 Just like owning a top end sports car, a piece of performance clothing 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 Midlayer to keep it performing at its best. It is important to follow the Product Care Instructions and use the correct wash  product as these can affect your clothing’s performance. In the case of CORE, we recommend turning it inside out and doing up all zips. Also avoid washing with other clothing that uses velcro. Care Guide Here

Pullover or zipped?

We use a combination of pullover and zipped styles in our Midlayers. Which you prefer comes down to personal preference and end use. A pullover tends to be lighter (no zips to weigh you down) but may be more awkward to pull on and off when the need arises. A full zip means its easy to pull on and allows for venting but it adds a little more bulk and the fit tends to be not quite as close and lots of zipped layers under a zipped shell can mean a stack of zipper pulls under your chin. Either way, both will do the trick, its up to you to decide!

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