Since it hit shelves in 2017 (Polartec first developed ... of polyester threads with tufts of fleece interspersed throughout the fabric. (In lighter weights, Alpha Direct is basically see-through.) ...

A mountaineer wears a Patagonia 1/4 zip made with Polartec 200 weight fleece, circa early 1990s. Photograph Courtesy Milliken It was an incredible breakthrough, one that Karstad remembers well.

It gets its warmth from its Polartec Classic 300-weight fleece material, not to mention an additional layer of windproofing around the neck and shoulders; thankfully, there are also pit zips for ...