Icebreaker Merino Weights Explained
Every Icebreaker baselayer and tee carries a number — 150, 200, 260, 300 — and once you know what it means, choosing the right layer takes seconds. The number is the fabric weight in grams per square metre (gsm). Lower is lighter and cooler; higher is warmer and denser. Here's how the range actually breaks down, and which weight suits which day out.
What the gsm number tells you
Fabric weight is the single best predictor of warmth in a merino layer. It doesn't tell you everything — knit structure and fit matter too — but for Icebreaker's range it's the shortcut that gets you 90% of the way to the right choice. Think of it as a dial from "cool and fast-drying" to "warm and cosseting".
Cool-Lite & 125 — the lightest
Cool-Lite blends merino with plant-based fibre (Tencel/lyocell) for the fastest-drying, most breathable fabric Icebreaker makes. This is warm-weather and high-output territory: summer hillwalking, trail days, travel in hot climates. It's the fabric behind the Cool-Lite Sphere tees. If you overheat easily or you're moving hard, start here.
150 Tech Lite — everyday merino
150gsm is the lightest pure-merino weight, and it's the everyday t-shirt of the range. Breathable enough for active use in mild conditions, soft enough to live in off the hill. The 150 Tech Lite III tee and polo are the staples here. Great as a standalone tee or a very light baselayer in spring and autumn.
200 Oasis — the do-everything midweight
If you buy one Icebreaker baselayer, it's usually a 200. Oasis 200 is the year-round midweight: warm enough for Irish winter hillwalking under a fleece, not so warm it's useless in the shoulder seasons. It's the most versatile layering piece Icebreaker makes, which is why it comes in crew, long-sleeve and half-zip. The Icebreaker baselayers collection is built around it.
200 & 260 ZoneKnit — same warmth, more venting
ZoneKnit takes the 200 or 260 weight and adds body-mapped ventilation panels at the back, underarms and lower torso to dump heat when you're working hard. If you run hot, do stop-start activity, or want a baselayer that copes with big efforts, ZoneKnit breathes better than the plain Oasis at the same weight. For steady, everyday layering, plain Oasis is simpler and cheaper.
260 Tech — cold-day warmth
260gsm steps things up for genuinely cold, still conditions and lower-intensity days — winter walking, cold commutes, ski touring at an easy pace, or anyone who simply feels the cold. The 260 Tech tops and thermal leggings are the go-to. Warm with minimal bulk, but you'll cook in them on a hard summer effort.
MerinoFine 300 — the warmest
The heaviest weight, reserved for the coldest days and the most static conditions. Overkill for most Irish use, but the right call for genuinely cold environments and low-output cold exposure.
The quick answer
Moving hard or warm weather? Cool-Lite or 150. One layer to cover most of the year? 200 Oasis. Cold, still days? 260 Tech. Run hot on the uphill? ZoneKnit. When you've settled on a weight, browse the full range in the Icebreaker baselayers collection, or see everything the brand makes on the Icebreaker page. New to merino altogether? Our Ultimate Guide to Merino Wool covers the fibre itself.
