Gear Review: Sierra Designs Isotope Nano Rain Jacket

The lightest jacket in our under-$100 test.


“The T-shirt I wore underneath it weighs more than this shell!” exclaims one tester. Ounce counters and hikers who see infrequent rain will love the Nano’s wispy-light 30-denier fabric and bare-bones approach to features (SD strips away all but a single Napoleon pocket, a fuzzy chin guard, and Velcro cuffs). But don’t underestimate the proprietary NanoLite two-layer fabric.

“It’s completely waterproof and adequately breathable for typical three-season backpacking conditions, like when I was cruising rainy foothills in the central Cascades,” says a tester. But when the trail steepened (gaining 1,000 feet per mile) and the temperature climbed to the high 60s, the so-so breathability and weight-saving lack of pit zips and other venting options made the shell stifling.

Fit is on the trim side, with just enough room for a light midlayer underneath, but articulated shoulders and arms ensure you stay covered during reachy maneuvers. Cautions: The hood proved floppy in high winds, and the featherweight fabric is not the best choice for hard and daily use.