Borah Gear Ultralight Bivy Review

Overview

The Borah Gear Ultralight Bivy is a no-frills, made-to-order bivy sack aimed at tarp campers, cowboy campers, and anyone trying to trim ounces from their sleep system. It’s built from Argon ripstop nylon in your choice of two weights, with a bug-netting face panel and either a chest or side-entry zipper. This isn’t a standalone shelter — it’s a supplement to a tarp, a quilt, or just the open sky, and it’s best suited to hikers who already know how they like to sleep and want a light, customizable layer around their bag.

Key Specs

Spec	Detail
Weight (chest zipper)	5.0 oz (~142 g)
Weight (side zipper)	5.3 oz (~150 g)
Fabric options	Argon67 or Argon90 DWR-coated ripstop nylon
Zipper options	Chest zipper or side zipper
Size options	Standard or Long length; Standard or Wide width
Custom sizing	Available on request
Made in	Montana, USA

Performance

The core trade-off with any Borah bivy is the one baked into the fabric choice. Argon67 and Argon90 are ripstop DWR coated nylon fabrics that both have excellent breathability, with the 90 being slightly more water resistant than the 67. That’s the whole calculus: go lighter and more breathable with the 67, or trade a bit of weight for a touch more splash protection with the 90. Forum users echo this — one hammock forums thread testing both side by side concluded that Argon67 would be lighter, cost slightly more, and be slightly more breathable than Argon90, though the difference was subtle enough that testers had to repeat their “candle test” a few times to be sure they weren’t imagining it.

Neither fabric is waterproof, and Borah doesn’t pretend otherwise — this is a splash-and-draft bivy meant to pair with a tarp, not a substitute for one. A long-term user on Backpacking Light’s forum ran an informal water-glass test on Argon67 and found it held up fine short-term: after a half hour there was only a very thin film of moisture on the underside of the fabric, and even after eight hours the fabric never leaked any drops in to the bottom of the glass. That tracks with what I’d expect from a DWR ripstop — good for dew, mist, and incidental splash, not for sustained rain without a tarp overhead.

Condensation is the more realistic complaint. One reviewer who used the bivy on a 10-day bikepacking trip under a tarp found condensation building up on cold, still nights — there was condensation on the shell of my sleeping bag and under the bivy after a calm, above-freezing night. That’s a near-universal bivy problem, not unique to Borah, but it’s worth knowing going in: on dead-calm nights, expect some moisture management regardless of fabric.

On sizing and fit, Borah’s a la carte approach is one of the bivy’s biggest strengths and occasional headaches. You pick length (standard to 6’1”, long to 6’4”), width (standard or wide), and zipper placement, and the company will customize further on request. One long-time owner on WhiteBlaze noted Borah were willing to customize the length for free as I wanted it shorter after I saw it since I was using a 8’ tarp so being longer than needed is a liability — that kind of flexibility is rare at this price point. The same reviewer did flag a quality gap versus pricier competitors, saying they’d would likely go with MLD if the extra money wasn’t an issue if the weight was similar, and noted their unit came in heavier then listed on website by 0.4oz due to material weight variations — a reminder that small-batch cottage gear can run a bit off-spec.

Packed size is a genuine highlight: multiple sources note it compresses down to roughly the size of a water bottle in its included stuff sack, which makes it an easy “why not just bring it” addition even on trips where you’re not sure you’ll need it.

Pros & Cons

Pros

• Genuinely light — 5.0-5.3 oz puts it near the top of the class for full-length bivies
• Two fabric weights let you dial in breathability vs. water resistance
• Free-standing customization (length, width, zipper style, stake-outs) that’s hard to find off-the-shelf
• Packs down to about the size of a water bottle
• Made in the USA by a small shop that’s responsive to custom requests

Cons

• Not waterproof — needs a tarp overhead in real rain
• Condensation on calm, cold nights is a real issue, as with most single-wall bivies
• Reported unit-to-unit weight variance due to small-batch fabric cutting
• Some users find the fit and finish a step below premium cottage makers like MLD
• No pole/hoop structure, so the face netting can sag onto your nose in still air

Who Should Buy This

This bivy makes sense for tarp campers and cowboy campers who want a light bug and splash barrier without committing to a fully enclosed tent, and for hikers who already know their preferred length, width, and zipper placement and want to have it built to spec. It’s less appealing if you want a truly waterproof standalone shelter or if you’re not willing to tolerate occasional condensation on still nights.

Verdict

The Borah Ultralight Bivy delivers on its core promise — a genuinely light, packable, customizable bivy from a small U.S. maker — but it’s a supplement to your tarp and sleep system, not a replacement for good site selection or ventilation habits. I’d rate it a 7.5/10: excellent value and flexibility for the tarp-and-bivy crowd, with the caveat that it demands the same condensation management as any single-wall bivy and isn’t going to out-finish pricier cottage competitors.