We call it the "72-Hour Collection" because every piece is built with the comfort, durability, and odor-resistance to last three days of nonstop wear. Even more, the incredibly soft merino wool is infused with the strength of nylon to ensure it never shrinks in the wash. Just a little heavier than your average t-shirt, you can use the UPF Quarter Zip for sun protection in warm weather or as an extra layer when the mercury drops.