When you up the training to two-a-days, polyester just doesn’t cut it. Even the lightest early morning shake-out will leave a synthetic top in need of a wash. Less than ideal when you run to work and still have an interval session scheduled for the evening.

Our Merino-nylon blend is practically impervious to odor even if you never choose to wash it. And we tested it the hard way, running morning and evening through the dog days of the Boston summer. One run? No problem. A week of runs? Still funk-free. One month without a wash? Put it this way: we lost our nerve long before this natural fabric showed any sign of losing its battle against bacteria.