Base Layers

Base Layers at Arc’teryx

A base layer works against your skin, moving moisture away and holding a little warmth in. Our range runs from merino wool to brushed knits, and the right one depends on how hard you work and how cold it gets.

What’s the difference between Rho Merino and Satoro merino wool base layers?

A merino wool base layer regulates temperature and resists odour, which is why it suits multi-day trips. The men’s Rho Merino Wool tops and bottoms wrap Merino fibres around a nylon core for durability, with elastane for stretch and shape. The women’s Satoro Merino Wool Crew Neck uses 240GSM Merino with minimised seams to reduce irritation, and the Satoro Bottom is made from Responsible Wool Standard certified Merino. Add merino wool hiking socks for the same benefits at your feet.

Which base layer tops suit cold starts and snow days?

Kyanite, our warm base layer range, is made from Polartec Power Stretch Pro, which stretches while you move while its brushed interior traps heat when you stop. The smooth nylon face slides under a jacket, and the women’s crew has thumbholes that keep the sleeves in place. For men, the Rho SV Zip Neck has a hollow-core build that stays breathable on high-output climbs and descents, with an extended collar that opens for ventilation or closes for coverage.

Which lightweight base layer tops suit mixed-output days?

The Rho LT line is a lightweight base layer made for lower-output days when it is cool to cold. Its Torrent fabric has a brushed surface for soft, next-to-skin comfort and moves moisture quickly, and a Polygiene treatment helps control odour. The LT Zip Neck adds a deep front zip, a tall collar and a chest pocket for your phone. Wear it under a jacket and GORE-TEX pants on snow.

Base Layer FAQs

Is a merino wool base layer too warm for New Zealand conditions?

Not if you match the weight to the day. Our Layering Guide says lighter weights suit warm conditions and high output, and heavier ones suit cool conditions or lower effort. Merino also resists odour and keeps its warmth when wet. Arc’teryx describes the Rho Merino Wool Crew Neck as a lightweight Merino wool layer, a sensible pick for milder days. Read the full layering guide.

What does GSM mean on a merino wool base layer?

GSM is grams per square metre of fabric, so a higher number is a heavier, warmer base layer. Our Merino tops, such as the Rho Merino Wool Crew Neck and Satoro Crew Neck, use 240GSM Merino. Lighter weights suit warm or high-output days, and heavier ones suit cool days or lower effort.

Is a base layer the same as thermals?

A base layer is the thin, fitted layer next to your skin that moves moisture and adds a little warmth, which is what most people mean by thermals. If you want a warm jacket to wear over it instead, browse insulated jackets or women’s insulated jackets.

Do I need base layer bottoms for hiking?

Only when it is cold or you will be standing still. On a frosty alpine start, base layer bottoms under hiking pants or women’s hiking pants stop the chill at rest stops. The Rho LT Bottom adds a gusseted crotch and a thigh pocket for a smartphone, and the Satoro Bottom has a high-rise waistband that holds a secure fit.