the OMM Core Vest

the OMM Core Vest

See our entire range from the OMM here!

The OMM Core Vest is an extremely lightweight and highly breathable insulation vest , developed for active use in the mountains where traditional insulation often gets too warm. It is part of OMM's innovative Core series , which is built entirely around PrimaLoft® Active , an insulating material that combines fleece-like warmth with more than half the weight reduction compared to classic fleece.

The vest is constructed from synthetic insulation fibers (plumes) woven directly through an open mesh material . This structure creates very high loft and effective thermal insulation , while the material's almost total air permeability means that excess heat is quickly ventilated away. The result is a garment that can be worn during high activity without having to be removed , by instead regulating the temperature with a thin shell on top.

When combined with a lightweight windbreaker – such as OMM’s Sonic Windproof – the Core Vest becomes a surprisingly effective insulation layer with unbeatable warmth-to-weight performance. When you get too warm, simply open or remove the shell, while the Core Vest can stay on and continue to insulate when needed. This makes it a true “valley-to-summit” garment , suited for fast rides where terrain, weather and intensity change.

Core Vest works equally well wet or dry . PrimaLoft® Active insulates even in moisture and has very good moisture transport , which means that the garment dries quickly and does not feel cold against the skin after sweaty climbs or rainy sessions. It can be worn as a very warm first layer in extreme cold , or as an insulating mid-layer over a thin base layer.

Weighing only about 72 grams, the Core Vest is one of the lightest ways you can add significant warmth around the core of your torso , without significantly affecting pack weight or freedom of movement.

Features & Benefits

PrimaLoft® Active 75 g/m² – extreme warmth in an ultra-light format

Very high breathability – ideal during high intensity

Weighs approximately 72 g – almost non-existent pack weight

Insulates even when wet – safe function in humid environments

Perfect with shell garments – unbeatable warmth-to-weight in layers

Valley-to-peak function – customizable throughout the entire trip

Features

Synthetic insulation vest

PrimaLoft® Active insulation (75 g/m²)

Flatlock seams positioned away from the shoulders for reduced chafing

Softly rolled collar

Reflective logo

Very low bulk – easy to combine with other layers

Technical specifications

Weight : approx. 72 g (M)

Insulation : PrimaLoft® Active 75 g/m²

Material : PrimaLoft® Active mesh construction

Fit : Fitted / Performance

Sustainability : 58% recycled material , Bluesign® & OEKO‑TEX® certified

Sizes : XS – XL

Suitable for

Mountain running, fastpacking, ultra-running, Mountain Marathons and intense mountain tours – when you want maximum warmth around the core of your torso without risking overheating .

Care instructions

Wash according to manufacturer's instructions. Air dry. Store uncompressed for best insulation performance.

The OMM Core Vest is a lightweight, sleeveless, body-hugging insulation vest that can be worn directly against the skin as a warm first layer or over a thin base layer as an insulating mid-layer.

Size chart

Measurements refer to the body, not the garment itself. Chest measurement should guide size selection, while waist measurement and body length are used as supplementary guidance.

How is the OMM Core Vest sized?

The Core Vest has a body-hugging and athletic fit . The vest should follow the upper body without large air pockets or loose material, but must not restrict breathing or movement in the shoulders.

The model may feel slightly smaller and narrower than the corresponding size from several other outdoor brands. This is especially true if the vest is to be worn over another garment.

Fit example

Published fit examples show the following:

• A person who is 172 cm tall and weighs 62 kg experiences size S as close-fitting and normal in fit.
• The same person experiences size M as slightly roomier but still well-fitting.
• An external retailer recommends considering a larger size as the Core Vest may feel smaller than other brands.

The examples are only indicative as chest circumference, body shape and planned layers affect the fit.

Our size recommendation

Choose size based on how you will use the vest:

• For use directly against the skin: normally choose the size that corresponds to your chest circumference.
• Over a thin base layer: choose your regular size if you are in the middle of the measurement range.
• As a mid-layer: choose the larger size if you are between two sizes.
• If you prefer a less body-hugging fit, you can choose the smaller size, provided that your chest and waist measurements are within the range.
• If you need extra space over your chest, stomach or shoulders, we recommend going up one size.

How do you measure?

Chest circumference

Measure around the widest part of your chest. The tape measure should lie flat and close to your body without being tight. Measure over the layer you plan to wear underneath the vest.

Waist

Measure around the narrowest part of your torso. Keep your stomach relaxed and let the measuring tape follow your body without tension.

Body length

Measure your height without shoes. Body length will help you judge the length of the garment, but chest circumference should guide your size selection.

Check the fit

The Core Vest fits correctly when:

• the material follows the upper body without large folds,
• the vest is not tight across the chest,
• the sleeve openings lie close to the body without cutting in,
• you can lift and rotate your arms freely,
• the bottom edge stays in place during movement,
• You have room for planned layers above and below the vest.