ltm [sn] x ltm Winter Seasons Long T

A winter base layer from ltm × [sn], built for swinging temperatures

Born from a collaboration between life time mountaineering (Kotaro) and Super.Natural, this long-sleeve base layer is built for winter movement. Having tried over 40 base layers, the developer set out to make "the one" piece that could handle the temperature swings common in winter mountains — often -5°C to +5°C in a single outing. Pure wool regulates temperature well but dries slowly, which can lead to sweat-chill during breaks, so this piece leans into keeping wool's strengths while adding faster drying.

Fabric design: 53% merino / 47% polyester (NIKKE AXIO)

A blend of 53% Australian merino wool and 47% polyester. Australian merino makes up only around 10% of global wool production, and at 18.5 microns it's fine enough to feel soft against skin and resist itching even over long days out. Merino regulates temperature and moisture well and helps control odor after wear, making it easy to manage on multi-day treks where you want to change layers as little as possible.

Synthetic fiber, on the other hand, excels at drying quickly during activity or after getting wet. Blending in 47% polyester keeps wool's warmth and moisture control while significantly boosting drying speed. The yarn is NIKKE AXIO, knit in a rib structure that offers more stretch, smoothness, a bit more thickness, and better durability than the stockinette knit used in most base layers. Fabric weight is 195g/m², a solid base for winter layering. Final finishing happens in Bishu, Japan, using soft water — a careful process that brings out the fabric's character.

Details built for winter movement

• Raglan sleeves: diagonal seaming from the neck to the underarm keeps arm mobility free and reduces interference with backpack shoulder straps.
• Y-joint sleeve construction: a pattern that doesn't restrict shoulder movement and resists riding up when you reach overhead.
• Thumbholes: cover the wrists and backs of the hands for warmth, helpful even during short stretches working with gloves off.
• Flat-seam construction: reduces seam bulk against the skin while strengthening the seams themselves.

Balancing temperature/moisture control with fast drying

Merino's temperature and moisture regulation, combined with polyester's quick-drying properties, is aimed at smoothing out the swing between working up a sweat and cooling down at a stop. Designed around the kind of -5°C to +5°C swings common in winter, it suits anyone who wants to adjust layers less often during winter hiking or mountaineering, where moving and stopping alternate throughout the day. How it feels will vary with activity level, wind, and the individual, so adjust with a mid-layer or shell as needed.

Fit and sizing

Unisex sizing. There's a notable size difference between S and M, especially in body length and sleeve length. If sleeve length and hem fit matter to you, check the height reference chart. Choose your color from the product options (4 colors available).

Specs