Research by ISLab.
Merino begins as a fineness. For centuries the sheep were bred in the Spanish highlands for fibre so fine that exporting the animal was a crime punishable by death, and Spain held that monopoly until 1765. Fineness is measured in microns, and the number explains the feel: the wool of childhood sweaters runs 32 microns and coarser, thick enough that each fibre end presses into the skin rather than bending against it, while ours sits at 17.5. The itch was never wool. It was diameter.
Twenty-six sheep reached Australia in 1797 by way of the Cape of Good Hope, and the breeding for fineness carried on there. Ours is Australian.
A fibre that works in both directions
Wool is keratin, the same protein as hair and nails, and it behaves less like a textile than like a small climate. It takes on up to 35% of its own weight in moisture before it feels wet against the body, and it gives off heat as it absorbs, which is why merino warms rather than chills in cold damp air. The sweat goes into the fibre instead of sitting on you.
What that means at 6 AM
A run that starts at five degrees and finishes at fifteen usually costs a layer decision at the door. In merino the decision mostly disappears: the fabric holds warmth through the first cold kilometres, opens up as the effort builds, and the sweat of the last stretch leaves the skin instead of pooling against it.
Several runs into a week, the shirt still smells like nothing. Merino binds odour compounds inside the fibre, where bacteria do not thrive, rather than leaving them on the surface. Nothing is applied to make that happen. It is the structure of the fibre itself.
MerinoBalance
Ours is MerinoBalance™: Australian merino at 17.5 microns, blended half-and-half with modal into a 140 GSM jersey rated −5°C to 20°C, with raglan sleeves and flatlock seams that keep the surface smooth where an arm swing or a pack strap would otherwise find a ridge. It belongs to Pace_System, the daily training end of the catalogue.
That temperature range did not come off a datasheet. It is where the piece actually worked, across a full season of wear-testing before Version 1.0 shipped in September 2025, which is why it is narrow and specific rather than all-season. Merino also softens with wear. The more you run in it, the better it sits.
The NaturalContact standard
NaturalContact™ is not a fabric. It is a standard we hold the pieces designed for direct skin contact to: natural fibres against the body, nothing synthetic on the skin over long efforts, and odour resistance that comes from the fibre rather than from a treatment. The Lightweight Merino Running LS carries it.
The layer against the skin is the one you live in for the whole run, from the cold at the door to the kilometre where you are finally warm, and it is the only equipment you never stop touching. So that is where we start. The right material supports the practice, then disappears.