Review: Sea to Summit Alto TR2 Ultralight Backpacking Tent

Ultralight Backpacking Tent
Sea to Summit Alto TR2
$449, 2 lbs. 9 oz. (rainfly, tent, and poles)
backcountry.com

Backpacking five days in September through some of the northernmost mountains in the Lower 48 in Washington’s Pasayten Wilderness—sharing the trails with Pacific Crest Trail thru-hikers finishing up their 2,650-mile walk as well as backpackers on shorter journeys—we wanted a shelter that could protect us from the wildest, late-season weather possible. It would also be nice if it wasn’t too heavy, given the rugged terrain there. Sea to Summit’s Alto TR2 fit the bill and demonstrated its cred as an outstanding ultralight tent.

A two-person, two-door, semi-freestanding, double-wall tent, the Alto TR2 kept my wife and me dry inside during a couple hours of early-morning rain, and it held up quite well in moderate winds on some nights, including at one campsite in a meadow just above Rock Pass on the PCT.


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Sea to Summit Alto TR2 ultralight backpacking tent.
Sea to Summit Alto TR2 ultralight backpacking tent.

“Semi-freestanding” may sound like an oxymoron, but it simply means that the tent’s pole structure gives it shape but pitching the tent properly nonetheless requires staking it out. In practice, even freestanding tents require staking for optimal performance, so semi-freestanding confers the advantage of reduced overall tent weight without compromising stability. Conveniently, you can also still flip the tent upside-down and shake dirt and debris out before removing the poles when packing it up—something that’s hard to do with a fully non-freestanding tent.

The Alto TR2 is fairly easy to pitch once you get the hang of the proper sequence—which I practiced in my yard pre-trip—but still took me several minutes in the backcountry. The hubbed pole system is shaped like a wishbone with one long ridgeline pole running the tent’s length, spliced into two short poles at the foot end, and a “tension ridge” bridge pole crossing over the high point to hold up both tent doors. Two adjustable guylines smartly connect very easily via toggles through loops at the tent ends to increase stability in wind.

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Sea to Summit Alto TR2 ultralight backpacking tent interior.
Sea to Summit Alto TR2 ultralight backpacking tent interior.

By staking out the center of the head end and the two corners at the foot end first, then erecting the poles and clipping up the tent’s mesh canopy before staking out the rest of the tent’s perimeter, and finally adjusting the tension on the seven stake points (including the two vestibules), it’s simple to achieve a balanced tension that keeps the floor and walls taunt. The pole and tent grommets are color-coded where the pole’s three endpoints are inserted into two grommets at the foot end and one at the head end. The two pockets on the underside of the rainfly are also color-coded to match the two ends of the tension ridge pole, allowing you to quickly align the rainfly.

But most uniquely, the upward tilt of the arms of the tension ridge that extends over both doors magnifies the living space—especially headroom—compared to many two-person tents in this weight class. It feels larger inside than the 27 square feet of floor space implies, while the 42.5-inch peak height exceeds what you’ll find even in many heavier backpacking tents. Overall interior space is modest but comfortable for two people—wide enough for two standard air mattresses (53 inches at its widest, 38 inches at the foot end) and 84 inches long, fitting even very tall people.

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Sea to Summit Alto TR2 ultralight backpacking tent.
Sea to Summit Alto TR2 ultralight backpacking tent.

The interior tent doors have two-way zippers and are tall and broad, making entry and egress very easy. The vertical walls create a drip line that keeps rain out of the tent interior in a light shower but wind can easily blow rain inside unless you close the vestibule doors at least partly.

The all-mesh interior provides excellent ventilation; we saw no condensation on cool, rainy mornings or cool, calm nights. Plus, the Alto TR2 creates very good high-low air movement from the multi-directional, covered apex vents at the rainfly’s very highest point—uniquely enabled by the tension ridge—and the baseline venting at the bottom enabled by two-way zippers on the vestibule doors that allow you to vent from the bottom without letting rain inside the interior shelter. A large, zippered panel directly below the apex vent, accessed from inside the tent, allows the free flow of air through that vent—and differs from high vents in other three-season tents in its position at the very top of the rainfly as well as in not having a mesh panel that inhibits air movement more significantly than you’d assume mesh would. (Want to learn more about the new S2S ultralight tents? Watch this lengthy but informative video.)

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Sea to Summit Alto TR2 ultralight backpacking tent door pull tabs.
Sea to Summit Alto TR2 ultralight backpacking tent door pull tabs.

The combined 18 square feet of storage area in the two vestibules compares with other tents in this weight class—adequate for storing boots and a midsize backpack. The tent doors can be rolled back completely on dry, mild nights for better air movement and stargazing.

The rainfly, tent floor, and mesh interior canopy are all made with 15-denier fabric—very lightweight but also more susceptible to tears than heavier fabric, so it warrants being careful in where you set it up and when packing it up. The deep bathtub floor keeps mud from splashing inside in a hard rain.

I like the little details like the upper pull tab on the two-way tent door zippers being shorter than the lower zipper tab, to differentiate between them in the dark; the horseshoe shape of the tiny rainfly clips that attach to the tent stake loops at three points, allowing you to easily connect and disconnect them with a quick 90-degree rotation; the adjustable lines that attach rainfly corners to the tent’s staked corners and the vestibule doors; and the separate stuff sacks for the rainfly and tent body (as well as the stakes and poles, as with most tents), more convenient for splitting up the tent’s components with a partner.

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Sea to Summit Alto TR2 tent rainfly vent.
Sea to Summit Alto TR2 tent rainfly vent.

The Alto TR2 Lightfoot footprint ($50, 8.4 oz., sold separately), allows you to leave the interior tent home and pitch the tent in bug-free weather with just poles, rainfly, and a waterproof floor made of more-durable, 68-denier polyester—a setup that shaves seven ounces from the shelter’s weight. The downside in a tent this small is that items you bring inside may more easily get pushed out from under the rainfly.

Other versions include the Alto TR1 solo tent ($399, 2 lbs. 1 oz.) and the Alto TR2 Plus ($489, 2 lbs. 13 oz.), constructed with fabric interior walls and a higher-specification waterproof floor for shoulder-season use in colder, wetter weather. And backpackers who prioritize space over low weight may prefer the Sea to Summit Telos TR2 ($499, 3 lbs. 4 oz.).

Sea to Summit Alto TR2

Space-to-Weight Ratio
Sturdiness
Ease of Use
Ventilation
Features
Value

The Verdict

At just an ounce over two-and-a-half pounds, the Sea to Summit Alto TR2 delivers surprising livability for an ultralight tent, along with good stability and ventilation, making it a great choice for ultralighters, thru-hikers, or anyone who prefers a lighter backpack without compromising on their shelter.

4.3

BUY IT NOW

You can support my work on this blog, at no cost to you, by clicking any of these affiliate links to purchase the Sea to Summit Alto TR2 at backcountry.com or seatosummit.com, the Sea to Summit Alto TR1 at backcountry.com or seatosummit.com, the Sea to Summit Alto TR2 Plus at backcountry.com or seatosummit.com, the Sea to Summit Alto TR1 Plus at backcountry.com or seatosummit.com, or the Sea to Summit Telos TR2 or another Telos version at backcountry.com or seatosummit.com.

See “The 8 (Very) Best Backpacking Tents” and all of my reviews of backpacking tents, ultralight backpacking tents, backpacking gear, and ultralight backpacking gear at The Big Outside.

See also my “5 Tips For Buying a Backpacking Tent” and “How to Choose the Best Ultralight Tent for You.” 

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Whether you’re a beginner or seasoned backpacker, you’ll learn new tricks for making all of your trips go better in my “12 Expert Tips for Planning a Backpacking Trip,” A Practical Guide to Lightweight and Ultralight Backpacking,” and “How to Know How Hard a Hike Will Be.” With a paid subscription to The Big Outside, you can read all of those three stories for free; if you don’t have a subscription, you can download the e-guide versions of “12 Expert Tips for Planning a Backpacking Trip,” the lightweight and ultralight backpacking guide, and “How to Know How Hard a Hike Will Be.”

NOTE: I tested gear for Backpacker magazine for 20 years. At The Big Outside, I review only what I consider the best outdoor gear and apparel. See The Big Outside’s Gear Reviews page for categorized menus of gear reviews and expert buying tips.

—Michael Lanza

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