Therm-A-Rest Boost 650 Review

Bottom Line

It’s rare that a new-to-market item lands in our top 3 so quickly, but the Therm-A-Rest Boost 650 bucks the trend. Senior Gear Analyst Ian Krammer fell in love with this bag over two dozen nights of car camping and backpacking across the Colorado Rockies in summer and fall. With a cushy feel, awesome features and a versatile design, it earns an Editor’s Pick on our camping sleeping bags guide.

The Boost 650 has a center zipper that expands the snug mummy shape to a roomy rectangular fit – perfect for staying warm while backpacking, or spreading out when car camping. It also has two armhole zippers. This design let us keep our shoulders and heads warm while reading a book – now that’s cozy. Soft nylon fabric, draft collars, and a massive stash pocket add to the comfort. We also appreciate that it’s light and packable, plus it comes in nearly every size for an impressively inclusive debut.

That said, all these zippers can feel like a bit much. This design is great for adaptability, but it’s overkill if you prefer a simple, no-fuss sleeping bag. It’s also not as warm as the comfort rating suggests and the mummy hood is a bit shallow, too, so we’d save this one for the 40-65°F range. Finally, the Boost 650 is a bit spendy. That said, it’s at the top of our list for a reason: this thing offers outstanding versatility that few other models can offer. If you want top-tier customizability and packability over simplicity, this is the one for you.

Comfort

The Boost 650 earns top marks for comfort from our testers because of its unique, comfy features. Our favorite? The Boost 650’s unique ability to unzip down the middle. This zipper allows it to expand from a snug, restrictive mummy that retains heat better to a more roomy, rectangular shape for more room overall. Senior Gear Analyst Ian Krammer is a very active sleeper, and the extra inches felt like a revelation on warmer nights switching between his side, back, and stomach. 

We’re also big fans of two zippered holes on top. They double as vents for dumping heat as well as armholes. We loved being able to stick our arms out while keeping our torso’s warm. Ian used these to read a book, scroll his phone, and more. The Boost 650 also has inclusive sizing including short, regular and long, as well as in wide sizes for each length. There’s a fit for nearly everyone.

That said, all those zippers can be a hassle when you just want to crawl into the bag to sleep. Several times, we’ve returned from a midnight bathroom break and unzipped the vent zipper or expanding zipper while trying to find the main zipper, which can be annoying. We find the mummy hood is great for retaining warmth, but it’s a bit snug and shallow. And, though the expansion feature creates more space, it’s still not as roomy as larger rectangular bags built purely for comfort. If you want maximum stretch-out space, there are better options, but for a balance of comfort and packability, the Boost 650 shines.

Warmth

The Boost 650 has one-of-a-kind ventilation and warming features. A bag-length zipper on top allows it to expand from a smaller, heat-efficient mummy shape – best for retaining heat down to 40°F – to a wider rectangle, best for warmer temps and more airflow. It has two vents on top that can be opened from the inside or outside, to not only fine-tune ventilation, but also serve as arm holes. Unlike many mummy bags, the full-length, 2-way side zipper extends all the way to the footbox, giving you extra control over airflow without sacrificing insulation.

The downside? Testing finds this bag’s temperature rating is ambitious. Ian slept on a frozen lake in this bag, combined with two high R-Value pads. The overnight temperatures dropped to 27°F. To stay warm he still had to put on base layers, midlayers, and a puffy.

The main culprit? There’s just a lot of zippers. This design increases the chance of cold air sneaking in compared to simpler designs, although the many draft tubes help. We also find the hood is a bit shallow, even for a mummy bag, so you may want to order a longer version to give yourself extra room. Still, these are small gripes. This bag is warm for most three-season camping trips.

Packed Size

Some sleeping bags eat up precious pack space, but not the Boost 650. Despite its many zippers, it compresses to just 20 inches by 7.5 inches in its stuff sack, making it one of the smaller picks on our list. It’s also one of the lightest when it comes to camping sleeping bags – only 2 pounds, 11 ounces.

Therm-A-Rest includes both a compression sack to squish the bag down tightly, as well as a separate mesh storage sack to maintain loft when not in use. Whether you’re heading deep into the backcountry or stuffing your trunk to the gills, the Boost 650 doesn’t take up much room.The tradeoff is that down insulation requires more upkeep compared to synthetic. It can’t be stored long-term in its compressed state, so you’ll need to give it space when not in use. Down also demands specific washing steps compared to synthetic insulation.

Features

The Boost 650 one is packed with clever designs. Ian loves the dual vents that double as armholes, perfect for dumping heat and reaching out of the bag quickly. A full-length zipper runs from the hood to the footbox, so we’re able to stick our feet out on warm nights. An expanding zipper transforms the bag from a heat-trapping mummy shape to a roomy rectangular layout. Long zipper pulls make adjustments easy, even with gloves on, and a snap closure at the top prevents the zipper from slipping open when moving at night.

We especially love the oversized internal pocket – this thing is deep – that easily fits a phone, headlamp and other small essentials. All these design elements make it a good fit for almost any sleeping style or temperature preference.

But, all those zippers can feel overwhelming, especially at night. When it’s dark, figuring out which zipper is which can be a little annoying if you prefer a more straightforward, no-fuss design. Additionally, Therm-A-Rest doesn’t include any zipper plows, so zippers are prone to snagging on the fabric. The interior pocket is spacious, but it lacks a closure, so smaller items like chapstick and car keys can slip out overnight if we toss and turn a lot. That said, if you want an extensive feature set for the ultimate versatility, the Boost 650 is one of the best.

Should You Buy the Therm-a-rest Boost 650?

For backpackers and car campers who want a feature-forward, lightweight bag that doesn’t skimp on comfort, go with the Boost 650. This bag cannot be beat for features, including excellent ventilation, arm holes, and an expanding shape that shifts from mummy to rectangular. This thing comes in a range of inclusive sizes. The lightweight design packs small for carrying deep into the backcountry on multi-day treks, but it’s got all the elements we look for in a solid car camping bag as well. Durable materials and draft tubes offer reliable warmth across three-seasons – and even mild winter nights. This bag delivers both convenience and comfort in a way few others can match.

That said, the Boost 650 is excessive for casual car campers who don’t need a high-performance, lightweight sleeping bag. The extensive feature set is impressive, but it adds unnecessary complexity if you just need a simple, warm place to sleep. The mummy hood is a bit shallow, and we find the comfort rating is closer to 40°F. This one is spendy, too, so budget-conscious campers may find better value elsewhere. But if you want an adaptable, lightweight, and ultra-functional bag for both frontcountry and backcountry use, the Boost 650 is an exciting addition to our car camping list.

What Other Backpacking Sleeping Bags Should You Consider?

If the Therm-A-Rest Boost 650 caught your eye, see how it compares on our best camping sleeping bags list. And while you’re here, consider these top competitors:

Kelty Cosmic Down 20 Review: The Kelty Cosmic Down 20 is a hit for those who want a high-performing bag for less money. It packs small and has warm down insulation for both backpacking and car camping, though it’s heavier.

NEMO Disco Endless Promise 30 Review: The NEMO Disco has similar ventilation features to the Boost 650, plus a very comfortable design. It’s more affordable and we also rate it a bit higher for comfort.

Mountain Hardwear Bishop Pass 15 Review: This one also uses quality down and features a mummy design. It’s warmer, simpler, and pricier, but the Bishop Pass 15 a premium and long-lasting choice with a more traditional feature set.