Never mind the Byzantine acronym: The five-letter name—and the technology built into these long johns—translates to perfect insulation for high-exertion winter adventures. The secret is a blend of Polartec Power Dry fabrics patterned to match the heat profiles of different zones on your body. The two styles of long-sleeve tops (pictured: the 1/4-Zip Mock T-Neck) place Polarweight Power Dry around your core, shoulders, and arms—the most exposed regions and thus the critical spots to insulate.
Testers say this gridded-microfleece poly is warm enough to wear alone while skinning uphill in 15°F cold with a big pack (and super-plush while sleeping). The less-vulnerable hip and inner-arm areas get Mid Weight Power Dry, while silky Tech Weight lines the armpits and forearms for maximum sweat and heat transfer. The tights (one style) follow suit, with Tech Weight cooling your crotch. “While hiking and skiing in subfreezing temps, the Thermal Zone kit let me maintain a better comfort equilibrium than any previous baselayers,” says one Colorado tester.
“My core stayed toasty and dried fast once I hit camp, and the barely-there pits vented a ton of heat.” Testers also raved about the fit (long and snug for draft-free coziness); packability (thanks to the ultralight Tech Weight panels); and no-chafe seams. Tops: $90-$100; 8.6 oz. (crew, tall XL); Bottoms: $85-$95; 6.7 oz. (tall L); m’s M-XXL, tall M-XXL; cabelas.com