The best-selling Swift Cap is for more than just training. Providing UPF 50+ sun protection on the crown of your head, and a full mesh liner for superior ventilation in warm weather, the Swift Cap packs in function and performance. Its shaped brim and nylon panels offer serious protection from the sun for runners and hikers, and its low profile fits nicely under a helmet for climbers and ski tours. Plus, weighing in at only 2.5 ounces, it’s ideal for the ounce-counting backpacker and thru-hiker. Adjustable headband - one size fits up to 24\" (61cm).