Zpacks Classic 20 Review – The Ultimate Ultralight Sleeping Bag?

Discover the Zpacks Classic 20 sleeping bag – a lightweight, warm, and versatile option perfect for ultralight backpackers seeking top performance in cold conditions.
Zpacks Classic 20

Zpacks Classic 20

Unpacking the Perfect Blend of Warmth, Weight, and Versatility
The Zpacks Classic 20 sleeping bag offers exceptional warmth, lightweight packability, and versatile features, making it an ideal choice for ultralight backpackers in cold conditions.


Warmth & Insulation
Packability & Weight
Comfort & Fit
Durability & Materials
Versatility & Features


  • Lightweight and packable
  • Excellent warmth and insulation
  • Versatile full-length zipper
  • Comfortable and roomy design
  • High-quality down fill


  • Premium price
  • Requires careful handling
  • Limited waterproofing
  • Few color options


Brief Overview

The Zpacks Classic 20 sleeping bag is a high-performance piece of gear designed for serious backpackers and outdoor enthusiasts. Known for its exceptional warmth-to-weight ratio, this sleeping bag is crafted to provide comfort in temperatures as low as 20°F (-6°C). Whether you’re embarking on a multi-day hike, a mountaineering expedition, or a backcountry camping trip, the Zpacks Classic 20 promises to be a reliable companion that won’t weigh you down.

Initial Impressions and Context of Testing

Upon unboxing the Zpacks Classic 20, the first thing that stands out is its impressively light weight and compact size. Weighing in at just 1.44 pounds (652 grams) and compressing down to a remarkably small volume, this sleeping bag is tailored for ultralight backpackers who prioritize both performance and portability. The craftsmanship is evident, with high-quality materials and meticulous stitching.

For this review, I tested the Zpacks Classic 20 on a five-day backpacking trip in the Rocky Mountains, where temperatures fluctuated between mild daytime warmth and freezing nighttime chills. The varied conditions provided an excellent opportunity to assess the sleeping bag’s performance across different weather scenarios. From its packability to its thermal efficiency, the Zpacks Classic 20 was put through its paces to determine if it lives up to its reputation as a top-tier sleeping bag for demanding outdoor adventures.

Technical Specifications

Key Features and Technology

The Zpacks Classic 20 sleeping bag is engineered with advanced materials and innovative design features that set it apart from conventional sleeping bags. Here are some of its standout characteristics:

  • Temperature Rating: Rated for 20°F (-6°C), this sleeping bag ensures warmth in cold conditions, making it suitable for three-season use.
  • Weight: At just 1.44 pounds (652 grams), it is remarkably lightweight, catering to ultralight backpackers.
  • Fill Power: Insulated with 900 fill power goose down, providing superior warmth and compressibility.
  • Construction: Features a sewn-through construction to minimize weight and enhance packability.

Design and Materials

The Zpacks Classic 20 sleeping bag combines high-quality materials with thoughtful design to maximize performance and user comfort:

  • Shell and Liner Fabric: The shell is made from ultra-lightweight, water-resistant, and durable 7D ripstop nylon, while the liner is a soft 10D nylon for added comfort.
  • Down Insulation: Uses ethically sourced, Responsible Down Standard (RDS) certified 900 fill power goose down, known for its excellent loft and insulation properties.
  • Zipper: Equipped with a full-length zipper that allows for easy entry and exit, and enables the bag to be fully opened and used as a quilt in warmer conditions.

Additional Features

  • Hood Design: The contoured hood offers additional warmth retention around the head, with a drawcord adjustment for a snug fit.
  • Draft Collar and Draft Tube: Includes a draft collar around the neck and a draft tube along the zipper to prevent cold air from seeping in, ensuring maximum heat retention.
  • Footbox: A spacious footbox designed to keep feet comfortable and warm, with enough room for natural foot movement.
  • Stuff Sack: Comes with a compression stuff sack that reduces the packed size to a minimal volume, making it easy to fit into any backpack.

Dimensions and Fit

  • Length: Available in multiple lengths to accommodate different heights (Short, Regular, Long).
  • Width: Offers a generous girth for ample space, ensuring comfort without the restrictive feel of some ultralight sleeping bags.

The Zpacks Classic 20 sleeping bag’s technical specifications highlight its balance of minimal weight and maximal warmth, making it a top choice for backpackers seeking reliable and efficient gear for cold weather adventures.

Performance Evaluation

Fabric Performance

Breathability: The Zpacks Classic 20 excels in breathability thanks to its 7D ripstop nylon shell and 10D nylon liner. These materials allow moisture from perspiration to escape while retaining warmth, keeping the interior of the sleeping bag dry and comfortable throughout the night.

Waterproofing: While the Zpacks Classic 20 is not entirely waterproof, its shell fabric is water-resistant, offering adequate protection against light moisture and condensation. During the Rocky Mountain trip, the sleeping bag effectively repelled dew and minor drizzles, keeping the down insulation dry and efficient.

Durability: Despite its ultralight construction, the Zpacks Classic 20 is surprisingly durable. The 7D ripstop nylon shell can withstand the rigors of backcountry use, including rough handling and occasional contact with abrasive surfaces. After multiple uses, the sleeping bag showed minimal signs of wear and maintained its structural integrity.

Weather Resistance

The Zpacks Classic 20 performed admirably in various weather conditions. During the Rocky Mountain test, nighttime temperatures dropped close to the bag’s lower limit, yet it provided sufficient warmth without cold spots. The sewn-through construction and high-quality down insulation ensured even heat distribution, crucial for cold weather camping.

In windy conditions, the bag’s contoured hood and draft collar effectively blocked out drafts, preventing heat loss around the head and neck. The draft tube along the zipper also minimized heat escape, ensuring a cozy interior even when the wind picked up.

Practical Features

Pockets: Although not a traditional feature of sleeping bags, the Zpacks Classic 20 includes a small internal pocket. This is perfect for keeping essentials like a headlamp, watch, or smartphone close at hand and protected from the cold.

Zippers: The full-length zipper is robust and operates smoothly, allowing for easy ventilation and access. It also enables the sleeping bag to be used as a quilt, which is a versatile feature for warmer nights or when sitting around camp.

Adjustments: The drawcord-adjustable hood and draft collar are practical additions that enhance the sleeping bag’s thermal efficiency. These adjustments allow for a customizable fit, ensuring maximum warmth and comfort by minimizing cold air infiltration.


One of the standout features of the Zpacks Classic 20 is its exceptional packability. The included compression stuff sack reduces the sleeping bag to a remarkably small size, making it easy to fit into any backpack. This compact nature, combined with its lightweight construction, makes the Zpacks Classic 20 an ideal choice for ultralight backpackers who need to maximize space and minimize weight without compromising on warmth and performance.

In summary, the Zpacks Classic 20 sleeping bag offers a combination of breathability, water resistance, durability, and practical features that make it a reliable and efficient choice for backpacking in cold conditions. Its performance in various weather scenarios demonstrates its versatility and effectiveness as a high-quality sleeping bag for serious outdoor enthusiasts.

Fit and Comfort

Sizing and Fit

The Zpacks Classic 20 sleeping bag is available in multiple lengths (Short, Regular, Long) to accommodate a range of heights. This variety ensures that users can select a size that fits their body type without excess material that could lead to cold spots or added weight. The Regular size, for instance, is designed to fit users up to 6 feet tall, providing ample space without being overly roomy.

The girth of the sleeping bag is also noteworthy. Unlike some ultralight sleeping bags that can feel constrictive, the Zpacks Classic 20 offers a generous width that allows for some movement inside the bag. This design caters to side sleepers and those who tend to shift positions during the night, ensuring they don’t feel trapped or uncomfortable.

Comfort During Various Activities

The Zpacks Classic 20 excels in providing comfort across a variety of outdoor activities, from high-altitude mountaineering to casual camping. Here’s how it performs in different scenarios:

Cold Weather Camping: During cold nights in the Rockies, the Zpacks Classic 20’s 900 fill power down insulation provided exceptional warmth. The contoured hood and draft collar effectively retained heat, while the spacious footbox ensured that my feet remained comfortable and warm throughout the night.

Warmer Conditions: On milder nights, the full-length zipper allowed for excellent ventilation. Unzipping the bag and using it as a quilt provided versatility, preventing overheating and ensuring comfort.

Extended Use: Over multiple nights of continuous use, the sleeping bag maintained its loft and comfort. The soft 10D nylon liner was gentle on the skin, preventing irritation even after prolonged contact. The high breathability of the fabric kept the interior dry, further enhancing comfort.

Personal Anecdotes and Quotes

During a particularly chilly night at an elevation of 10,000 feet, the Zpacks Classic 20 truly proved its worth. The temperatures dropped significantly, but the sleeping bag’s insulation kept me warm without the need for extra layers. The adjustable hood and draft collar were easy to use, even with gloved hands, ensuring a snug fit that trapped heat effectively.

Another instance of the bag’s comfort was during a warmer evening, where I appreciated the ability to unzip it fully and use it as a quilt. This feature is particularly useful for those who prefer more freedom of movement or for couples who wish to share sleeping space.

In conclusion, the Zpacks Classic 20 sleeping bag offers an excellent balance of fit and comfort, accommodating different body types and providing versatility for various outdoor conditions. Its thoughtful design ensures that users remain warm, dry, and comfortable, making it a standout choice for both ultralight backpackers and casual campers alike.

Pros and Cons


Lightweight and Packable One of the most significant advantages of the Zpacks Classic 20 is its ultralight weight. Weighing just 1.44 pounds (652 grams), it is ideal for backpackers who prioritize weight savings. Its compact pack size allows it to fit easily into any backpack, making it perfect for long treks and multi-day hikes where space and weight are at a premium.

Warmth and Insulation The 900 fill power goose down provides excellent warmth, with a temperature rating of 20°F (-6°C). This high-quality insulation ensures that users stay warm in cold conditions, making the bag suitable for three-season use.

Versatility The full-length zipper offers great versatility, allowing the sleeping bag to be used as a quilt in warmer conditions. This feature enhances its usability across a range of temperatures and activities, from cold mountain nights to mild summer evenings.

Comfort and Roominess With a generous girth, the Zpacks Classic 20 provides ample room for movement, catering to various sleeping positions. The contoured hood and draft collar add to the comfort by effectively sealing in warmth and preventing drafts.


Price The Zpacks Classic 20 comes with a premium price tag, which may be a barrier for budget-conscious hikers. While the quality and performance justify the cost, it might not be accessible to all outdoor enthusiasts.

Durability Concerns Despite the durable materials used, the ultralight 7D ripstop nylon shell may still be prone to wear and tear over extended use in rugged conditions. Users need to handle it with care to avoid damage.

Limited Waterproofing While the bag’s shell is water-resistant, it is not fully waterproof. This limitation means extra caution is needed in wet environments to ensure the down insulation remains dry and effective.

Lack of Color Options The Zpacks Classic 20 offers limited color choices, which might be a minor drawback for those who prefer more variety in their gear’s appearance.


The Zpacks Classic 20 sleeping bag offers a remarkable combination of lightweight construction, excellent warmth, and versatile design features. Its high performance makes it a top choice for serious backpackers, though the premium price and careful handling requirements might not suit everyone.

Comparative Analysis

The Zpacks Classic 20 sleeping bag stands out in the ultralight category with its impressive weight and warmth, but how does it compare to the Feathered Friends Swallow UL 20 and the REI Magma 15?

Feathered Friends Swallow UL 20 The Feathered Friends Swallow UL 20 is a direct competitor in the ultralight 20°F sleeping bag category. Weighing slightly more than the Zpacks Classic 20, the Swallow UL 20 comes in at approximately 1.75 pounds. It features 950+ fill power goose down, which offers excellent insulation and slightly higher loft compared to the Zpacks. The Swallow UL 20 also boasts a more traditional mummy shape with a full-length zipper and a well-designed hood. However, it is slightly less packable than the Zpacks Classic 20 due to its marginally heavier weight and bulkier construction. Both sleeping bags offer excellent warmth and durability, but the Zpacks has a slight edge in weight and compressibility, making it more suitable for ultralight backpackers.

REI Magma 15 The REI Magma 15 is another excellent option, designed for temperatures down to 15°F. It uses 850 fill power down, which is slightly lower than the Zpacks’ 900 fill power but still provides substantial warmth. The Magma 15 is known for its excellent balance between weight, warmth, and affordability, weighing around 1.75 pounds. It features a more traditional mummy design with a snug fit, which can be more restrictive than the Zpacks Classic 20’s roomier design. Additionally, the Magma 15 offers a more robust water-resistant treatment, making it slightly better suited for damp conditions. While the Magma 15 provides great value for money and a bit more warmth, the Zpacks Classic 20’s lighter weight and higher fill power make it a preferred choice for ultralight enthusiasts prioritizing packability and minimal weight.

In summary, while the Feathered Friends Swallow UL 20 and the REI Magma 15 are both exceptional sleeping bags in their own right, the Zpacks Classic 20 offers superior weight savings and compressibility, making it an excellent choice for ultralight backpackers seeking maximum efficiency in cold weather conditions.


The Zpacks Classic 20 sleeping bag is an exceptional choice for ultralight backpackers seeking a balance of warmth, weight, and packability. With its 900 fill power goose down, water-resistant 7D ripstop nylon shell, and versatile full-length zipper, this sleeping bag delivers top-notch performance in cold weather conditions down to 20°F (-6°C). Its lightweight design, weighing only 1.44 pounds, and compact pack size make it ideal for long treks and multi-day hikes.

While it comes with a premium price tag and requires careful handling due to its ultralight materials, the Zpacks Classic 20’s advantages in warmth, comfort, and versatility outweigh these drawbacks. This sleeping bag is best suited for serious outdoor enthusiasts who prioritize minimizing weight without sacrificing performance. Overall, the Zpacks Classic 20 stands out as a reliable, high-quality option for cold weather backpacking adventures.

Further reading