Outdoor Research Helium II Jacket Review

Overview

The Outdoor Research Helium II is a 180g (6.4 oz) ultralight rain shell built around a single mission: give you credible storm protection at the lowest possible weight penalty. It’s been a staple in the OR lineup for years, landing on “best ultralight rain jacket” lists from Backpackers.com to Outdoor Gear Lab — and for good reason. Weighing in at a scant 6.2 ounces for a men’s medium, it’s fully wind- and waterproof, decently well-featured, and fits the bill for both ultralight die-hards and comfort ultralighters. That said, it’s not trying to be a four-season fortress, and understanding that distinction is the whole ballgame.

Key Specs

Spec	Detail
Weight	180g / 6.4 oz (men’s medium)
Material	2.5-layer Pertex Shield DS Ripstop (30D nylon)
Waterproofing	Yes — DWR coated, fully seam-taped
Zippers	YKK AquaGuard water-resistant
Pockets	1 zip chest pocket (doubles as stuff sack) + internal mesh pocket
Hood	Adjustable with rear bungee, small bill
Cuffs	Half-elastic
Hem	Elastic drawcord (right-side adjustment)
Packed Size	~Fist-sized (with carabiner loop)
Extra Details	Reflective logos, carabiner loop
Comparison	See how the Helium II Jacket compares to similar gear

Performance

Waterproofing

The Helium II does its job in the conditions it was designed for. Up against moderate to light rain — and even when left with a puddle of water on top — the Helium does just fine. However, when tested in torrential downpours and high-pressure spray simulations, the fabric will get wet. That’s a fair and honest summary. One PCT hiker who put the jacket through roughly 200 miles of unusually wet Southern California desert conditions reported that shoulders and cuffs got pretty soaked under the jacket in a heavy driving sleet storm, while the front and back stayed really dry. The fully taped seams hold up well; the weak points are the cuffs (more on that below) and the DWR coating under pack contact. After almost continuous use, some of the coating had started to wear off under shoulder straps and the seam tape had started to come loose in areas of high abrasion. Worth knowing before a long trip — treat the DWR proactively.

Breathability

This is the Helium II’s biggest limitation, and it’s a known trade-off of 2.5-layer construction without pit zips. Breathability is just okay. When hiking uphill on the Wonderland Trail carrying a full pack, the Helium got a little clammy inside but was tolerable. On autumn trail runs of up to two hours, the hood could stay up in strong, cold wind without building up much moisture inside — mostly because of the lower exertion level. The pattern is consistent across reviewers: it’s fine for low-to-moderate output in cool conditions, and it starts to feel like a greenhouse when you’re grinding uphill in warm, sustained rain. There are no pit zips, so heat dissipation relies solely on fabric breathability. If you run hot or hike hard in wet weather, plan to vent by unzipping the front rather than counting on the membrane.

Wind Resistance

This is one area where the Helium II genuinely earns praise. The jacket is virtually windproof. It won’t keep you warm given how thin 30D fabric is, but by cutting out the wind, you can dramatically improve the performance of other layers. I’ve heard from multiple users who rely on it as a wind layer on ridgelines even when rain isn’t in the forecast — a legitimate second role that justifies the carry weight when skies are uncertain.

Packability

The party piece. When packed in its stuff sack pocket with a carabiner loop, this jacket measures a mere 4.5×4.5×3 inches (60.75 cubic inches), making it by far the most compact jacket in Outdoor Gear Lab’s test lineup. The carabiner loop earns its keep too — you can clip the stuffed jacket to the outside of a daypack or running vest so it’s immediately accessible without digging through your bag. It packs down to the size of a hamburger into its own pocket, complete with a small clip loop, so it’s easy to toss into a pack, clip to a harness, or strap to a hydration vest when the sun comes out.

Fit & Features

The cut is close but not slim — what Outdoor Research calls “Standard.” You can wear appropriate midlayers under the Helium II and still be comfortable in the high-20s.

If you’re planning to layer over a puffy, sizing up is a smart move. The hood adjusts cleanly with a single rear pull and

slips over a climbing helmet easily and stays in place even in strong winds.

The cuffs are the design decision I keep coming back to. In an effort to reduce weight, Outdoor Research uses a half-elastic to seal the cuffs. The problem is that the cuff hole is too big — it would be great with gloves, but without anything under at the wrist, the openings gape. Wind and some precipitation can get in when on the move. A hook-and-velcro closure would be a meaningful upgrade. For now, the workaround is simple: wear liner gloves when the weather turns ugly.

The pocket layout is worth flagging. There’s one zip chest pocket, which doubles as the stuff sack. This pocket opens inside the jacket, so you might put a small electronic device in there to better shield it from weather, but it would be inaccessible if worn under a pack hip belt. No hand warmer pockets — a deliberate weight trade-off, but one that bothers people who run cold hands. The main zipper pull is tiny and difficult to grab at times. Being so small, it sort of feels cheap, even though it’s a YKK zipper.

Pros & Cons

Pros

• Exceptional weight-to-protection ratio at 180g with full seam taping
• Stuffs to fist size; carabiner loop makes it genuinely grab-and-go
• Virtually windproof — earns a second life as a wind layer
• YKK AquaGuard zippers haven’t shown leakage in extended testing
• Adjustable hood fits over helmets, has a functional bill
• Reasonable price compared to Gore-Tex alternatives
• Reflective logos add low-light visibility — a small but appreciated touch

Cons

• Breathability is mediocre; clamminess during sustained aerobic effort in the rain
• No pit zips to compensate for limited breathability
• Half-elastic cuffs gap at the wrist — water and wind get in without gloves
• No hand pockets; chest pocket is inaccessible under a hip belt
• DWR and seam tape show wear under pack straps with heavy use
• Fiddly, small zipper pulls on the main front closure
• Not appropriate for sustained heavy rain or true alpine conditions

Who Should Buy This

The Helium II is purpose-built for ultralight backpackers, thru-hikers, and fastpackers who want a credible rain shell tucked in a corner of their pack “just in case.” It’s a good choice for warmer weather trips where gear weight is a priority and you’re unlikely to need a rain jacket, but feel you need to carry one anyway — a calculation that backpackers armed with weather forecasts make about shorter trips all the time. It also makes sense as a secondary shell for anyone doing multi-day trips in variable conditions. What it provides in incredibly small size and featherweight heft, it sacrifices in water resistance, so it may not be advisable if you plan on facing extreme weather conditions. If your itinerary includes sustained, multi-hour deluges — think Pacific Northwest in November — step up to a 3-layer shell.

Verdict

The Outdoor Research Helium II has earned its reputation as one of the great “just-in-case” shells in backpacking — it’s honest about what it is, and it executes that role better than almost anything at this weight. No jacket will keep you 100% dry while walking in the rain, but this one does about as good a job as any, at a fraction of the weight, which makes it easier to carry and more comfortable when packed away. The cuff design and mediocre breathability are genuine limitations, not nitpicks — but they don’t disqualify the jacket, they just define its lane. At 180g with full seam taping and legitimate storm credentials, it earns a 7.5/10 for anyone counting grams.