The Tree Runner immediately impresses with its lightweight feel and soft, flexible knit upper made from eucalyptus fiber (Tencel™ Lyocell). It feels noticeably cooler against the skin than the Wool Runner, making it exceptionally comfortable for sockless wear, especially in warm conditions. My Dubai testing confirmed this – after a 12,000-step day navigating crowded souks and then ducking into air-conditioned malls where the temperature was a good 40 degrees cooler, my feet stayed significantly drier and cooler than they would have in other sneakers. They really do let your feet breathe, which is a lifesaver in 95°F+ (35°C+) heat.\n\nLike its wool counterpart, however, the Tree Runner offers minimal arch support – basically zero for long hauls. The included insole is basic, and the unstructured knit upper doesn't provide much inherent stability. While comfortable for casual wear in the heat, they lack the support needed for demanding travel days involving extensive walking or standing on hard surfaces. Fit can also be tricky as Allbirds doesn't offer half sizes, and consistency between models varies. If you need serious support for museum marathons, these might not be your best bet, even if they keep you cool.