Gear Review: I/O Bio Merino Pilot Suit

A full-body baselayer (a.k.a. pilot or "union" suit) that's as warm as they come.

[warmest]

“This new-school union suit is now my second skin for skiing and cold-weather camping,” raves our tester, who wore the one-piece hoody on nights down to 4°F during winter skills classes with the Colorado Mountain Club. “The fine merino fabric is thin and breathable, and it naturally resists odor, so I never got clammy or smelly—not even after three days of snowshoeing, building snow caves and kitchens, and sleeping in the suit every night.”

And there’s not a hint of itch, thanks to supersoft 18-micron merino (the smaller the fibers, the softer the wool). The integrated hood works great under a helmet or hat; the long crotch zipper makes pee breaks easy; and thumb loops keep wrists protected. Bottom line: If you regularly camp in deep cold, this suit is a bargain. $160; 11.5 oz. (m’s XL); m’s S-XL, w’s XS to XL; io-bio.com