Boulder/Flatiron = Easy Fit - Good ease over body, slightly more room for an all day comfort fit, extra length for better waistline coverage, longer arms with thumb loops for better wrist coverage, mix of raglan/inset sleeves for chafe free pack usage, strategically placed underarm eyelet panels for better venting, can be used for any activity as well as everyday situations.
Goldhill/Darkhorse = Tech Fit - A close performance fit for maximum moisture transfer and thermal efficiency, extra length for better body coverage, longer arms for better wrist coverage, mix of raglan/inset sleeves for chafe free pack usage, strategically placed additional eyelet panels for increased venting and moisture transfer, best used for high output/aerobic activities either stand alone or as part of a laying system.