Hacking heat retention. The holy grail of natural fibers - our Japanese Merino wool is sourced from the world's highest credentialed ethical Merino farm in New Zealand. We specifically design for thermo-regulation while running so all Merino tees are cut on the bias to circulate airflow in a circular-pattern around the body rather than an upwards pattern. This avoids warm air escaping in the "up-down" motion of a runner's gait.