The Smartwool Intraknit(TM) Seamless Long-Sleeve builds ventilation directly into the knit instead of adding it as a separate panel, so the shirt breathes exactly where a high-output session needs it to. Merino wool and TENCEL(TM) Lyocell fiber handle moisture, temperature, and odor underneath that construction, while minimal seams keep the fabric from catching or rubbing through a full training session. A regular fit leaves room to move without adding bulk. What Our Gearhead(R) Experts Are Saying:"I've stopped checking my collar and underarms for hot spots halfway through a hard interval session. The seams just aren't there to catch on anything, so the only thing I notice is the workout."