Wool Clothing: Fabric, Construction and Technologies

Making the most comfortable outdoor clothing starts with using the best ingredients and technologies. We use thermal body mapping to create wool clothing that offers the right amount of Merino for maximum comfort and performance; more wool in areas where the body tends to chill and less where the body tends to run hot. And when the sport and outside elements require it, we add other high-performance fabrics to make our products even smarter.



Next-to-Skin Base Layers: Merino next to your skin works with your body’s own heating and cooling system to keep your core temperature where it should be.

To personalize your base layer system, we make two different base layers weights for active pursuits anywhere, in any weather.

Merino 150 (150gram)
Created for: Year-Round Base Layer

This 150g fabric is a year-round base layer that sits next to skin. It’s the first layer in the Smartwool layering system that works with the body’s natural cooling and heating systems. Merino 150 is made with Core Spun technology where Merino fibers are wrapped around a nylon core to increase durability while still keeping the comfort and benefits of Merino next to skin. Styles using this fabric include mild weather base layer tops and bottoms, casual tops and accessories.

Merino 250 (250 gram)
Created for: Cool to Cold Weather Base Layer

The second piece in the Smartwool layering system, Merino 250 is an ideal base layer for stop-and-go or cold weather activities where warmth and breathability are critical. This 250g fabric is incredibly soft, uses an interlock knit for warmth and loft without bulk, and naturally resists odors. Apparel made with this 100% Merino fabric include base layer bottoms, base layer tops and hoodies, and cold-weather accessories like beanies and gloves.

PhD® Ultra Light
Created For: High-Energy Activities in Warm Weather

This mild to warm weather fabric blends Merino and polyester to create the ultimate training gear. The unique blend boosts the benefits of Merino with better stretch and recovery, better shape retention and a faster dry time that Merino alone. Primed for sweaty workouts, apparel made from this fabric includes sports tanks, tees and long sleeves.  They’re ideal for warmer weather training and easily transition across seasons.

PhD Ultra Light

PhD® Light
Created For: High-Energy Activities in Cool Weather

PhD Light apparel brings the smarts from PhD Ultra Light like enhanced stretch and recovery, better shape retention and a faster dry time that Merino alone, to cooler weather. From performance tights to sport tops that protect against Mothers Nature’s many moods, these layers offer breathability and moisture management for aerobic uses in cool to cold weather. 

Created For:  High-Energy Activities in Cold Weather

SmartWool® PhD® fabric uses a unique kitting method that concentrates Merino against the skin and a nylon/elastane blend against the elements. Designed for cold weather activities where warmth is key and abrasion resistance a must, apparel made with this fabric includes performance tights.


SmartLoft (60 and 120 gram)
Created For: Cool to cold Weather Midlayers

Featuring proprietary wool insulation, PhD® SmartLoft products offer ultimate warmth while also remaining incredibly lightweight and compressible. Thanks to the magic of Merino, SmartLoft also helps regulates temperature, stays warm when wet and is machine washable. Designed from the inside out, SmartLoft layers start with a Merino lining to help keep you warm and dry. Then we add a wool insulated, wind-resistant face and DWR finish to handle the elements. Available in 60 and 120g weights, SmartLoft layers are offered in hoodies, vests and full zip midlayers.

Merino/TENCEL® blend
Created For: Travel and Everyday Adventures in Warm Weather

A lightweight blend of Merino and TENCEL® fiber that results in a softer, wrinkle-resistant, better drape than Merino alone. TENCEL®, a type of lyocell, is a biodegradable material made from wood pulp cellulose.

Recycled Wool
Created For: Layering in Cool to Cold Conditions

Following a centuries-old Italian tradition of re-purposing wool garments, our recycled wool fabric helps give gently used wool a new life. Discarded wool is sorted into color categories and then shred, helping to reduce energy use, especially water.


4 Degree™ Elite Fit System: Smartwool’s most advanced proprietary fit system found in all PhD® Performance socks.  The fit system includes four bands - ankle, arch, lower instep and upper instep – to keep the sock in place, provide faster flex and recovery and deliver an extraordinarily comfortable fit.

Indestructawool™ Technology: A patent-pending, wool-based durability construction method for exceptional durability and comfort. This three-step method places the right materials in the right place for the right reason, utilizing a nylon-reinforced exterior while keeping the comfort of Merino next to skin. Indestructawool® technology is found in PhD™ Performance socks.

Core Spun: Merino fibers wrapped around a nylon core for added durability while still keeping the comfort of Merino next to skin. Core Spun technology is used in Merino 150 apparel and accessories.

Virtually Seamless™ Toe: A smooth toe seam for ultimate in-shoe fit. This technology is found in performance and casual socks.


Through specialized knitting techniques, we’ve created fabrics that maximize the benefits of Merino wool.

Jersey: A universal knit stitch that is used for a variety of garments. Jersey knit is very stable and offers easy care, featuring a flat finish that doesn’t snag easily. We use a jersey knit in Merino 150 layers as well as casual sweaters. 

Stretch Jersey: With stretch jersey knit we add a touch of elastic to the fabric for improved shape retention. This also allows the garment to easily conform to the natural shape of the body without bunching or binding.

Rib Knit: A knit that has vertical wales similar to corduroy. This knit offers a lot of cross stretch and recovery and is very flattering to the body. Because of the fabric’s resilience, we are able to cut a garment closer to the body while still delivering an extraordinary comfortable fit. Smartwool sweaters use rib knit construction.

Interlock Knit: A very unique knit that looks like a grid or latticework. We use interlock because it offers really good cross stretch and recovery. It also has a little more loft to the stitch. This means more air is trapped in the knit structure, which creates a warm microclimate next to skin. The loft also adds incredible softness to the garment. Apparel that uses this type of knit includes Merino 250 base layers and accessories.