Plenty of ventilation and a smart feature set make the Flight Training Pack our top pick for speed demons. Unlike many tight-fitting running vests that trap sweat, breathability excels here. Credit the space-age fabric: Designers wove a durable, tight-knit Cordura nylon ripstop around a polka-dot pattern made of special “dissolving yarn,” which disintegrates in a chemical wash. What’s left behind is a mesh that’s both more breathable than similar fabrics, and also more durable thanks to the ultratight weave. The fabric proved a godsend for one tester who spent 14 miles hopping deadfall during the dog days of summer in Colorado’s Gore Range, as he never had to stop to cool down. A large, cinch-top dorsal pocket fits a light puffy, shell, and first-aid kit, while a zippered cell phone sleeve and four other pouches on the shoulder harness keep small essentials close at hand. The Flight Training Pack also comes with two half-liter water bottles, each with a pull-cord affixed to the bottom. The cord threads through the bottom of the chest pockets, so we could retract the bottles back into their sleeves with a single pull.