The Therm-a-Rest Parsec 20 is a high-quality sleeping bag filled with 900-fill hydrophobic duck down, ideal for three-season use. Its box-baffled construction keeps the down evenly distributed in individual pockets, preventing shifting, eliminating cold spots, and preserving maximum loft for consistent warmth. Combining sustainability, comfort, and packability, this bag offers outstanding performance at a competitive price.

• • Weight: 1 lb 13 oz (820 g) – we measured 1 lb 14.4 o (862 g)
  • Packed Dimensions: 7 x 10.5 in (18 x 27 cm)
  • Insulation: 900-fill PFAS-Free Hydrophobic Duck Down, RDS-certified
  • Fill Weight: 17 oz (490 g)
  • Construction: Box Baffles
  • User Fit Length: 72 in (183 cm)
  • Bag Length: 80 in (203 cm)
  • Girth (Shoulder / Hip / Footbox): 62 / 57 / 46 in (157 / 145 / 117 cm)
  • EN Comfort Rating: 29 °F (-1 °C)
  • EN Limit Rating: 18 °F (-8 °C)
  • Shell Fabric: 100% Recycled 20D Nylon Ripstop with DWR finish
  • Lining: 20D Nylon Ripstop
  • Zipper: Left side
  • Compression Sack: Included

Materials

The Parsec Hood features a beefy 360 draft collar

The Parsec 20 has a comfortable 20-denier nylon ripstop fabric for both the shell and lining. This fabric is lightweight yet durable, offering resistance to wear and tear while maintaining a soft hand feel. The durable water repellent (DWR) finish enhances resistance to moisture, helping the down insulation maintain loft even in damp conditions and dry faster.

The insulation is premium 900-fill power hydrophobic duck down treated without PFAS chemicals, reducing environmental impact and potential health concerns. Duck down is just as warm as goose down with the same fill power rating, but it's less expensive for manufacturers to source, which is why the Parsec is more reasonably priced than other options. The down is also RDS-certified, meaning it comes from waterfowl that were raised and harvested humanely. With a generous fill weight of 17 oz (490 g), the insulation provides ample warmth for three-season use.

Warmth and Temperature Ratings

The Parsec 20 is rated with an EN Comfort temperature of 29 °F (-1 °C) and an EN Limit rating of 18 °F (-8 °C). This means most campers, including women and those of smaller stature, will feel comfortable at just above freezing temperatures, while the limit rating indicates the lowest temperature at which a larger person or your average man might be safe without additional insulation. To their credit, Therm-a-Rest was one of the main proponents of industry-wide temperature-rating standards testing for sleeping bags, but given that this bag is marketed as a unisex bag, I think it'd be more transparent if it were named the Parsec 30 rather than the Parsec 20.

The Parsec 20 has YKK’s special anti-snag zipper slider.

With 80 inches of length, a shoulder girth of 62 inches, and a footbox girth of 46 inches, the Parsec's dimensions allow for comfortable movement inside the bag without feeling overly snug. However, smaller individuals, including women, may feel colder because more body heat will be required to “heat the bag up” once it's zipped closed.

Design Features and Comfort

The Parsec’s design prioritizes warmth retention and comfort. The sleeping bag has a three-fourths length left-hand zipper with a YKK antisnag zipper and a second zipper slider so you can vent warmth on warm nights. The zipper is backed by a beefy draft tube full of down insulation to prevent cold air from leaking through the zipper teeth and has a zipper garage and snap at the top. This offloads pressure on the zipper and also lets you unzip it from the top to vent excess warmth. Between the top zipper and the bottom zipper slider, the venting options on the Parsec 20 are really great.

The bag’s hood is cinchable to trap heat around the head effectively, an essential feature for maintaining warmth during cold nights. It has a 360-degree draft collar that surrounds the upper part of your chest and neck, preventing warm air from escaping when you wiggle at night.

The sleeping bag has a down-filled draft tube alongside the side zipper

One of the distinctive features of the Parsec is its baffled insulated footbox, designed with extra down insulation to concentrate heat around your toes, a common area of heat loss. This ergonomic feature adds noticeable comfort in cool conditions.

Finally, you’ll find a small stash pocket inside the sleeping bag that is ideal for storing small essentials like a headlamp or phone within easy reach.

Packability and Weight

At 1 lb 13 oz | 820 g (our sample was 1.4 ounces heavier), the Parsec 20 is impressively lightweight for a down sleeping bag with such generous insulation and interior room. It compresses down to a compact 7 x 10.5 inches (18 x 27 cm) in its included compression sack, making it a great choice for backpackers who want to minimize pack volume and use a smaller, lighter-weight backpack. While it’s not the absolute lightest bag in its class, the Parsec balances weight with durability and comfort features that justify the slight trade-off.

Comparable ultralight 15 and 20-degree sleeping bags

Recommendation

The Therm-a-Rest Parsec 20 is a versatile and well-crafted sleeping bag ideal for three-season use. Its 900-fill hydrophobic duck down provides excellent warmth and loft retention, while the box-baffled construction prevents shifting and cold spots. With features like an insulated draft-tube zipper, cinchable hood, and extra-insulated foot box, it delivers consistent comfort throughout the night. The use of recycled nylon ripstop fabric with a durable water repellent finish enhances durability and moisture resistance without adding weight, making it both practical and environmentally friendly.

While not the lightest option in its category, the Parsec 20 strikes a strong balance between warmth, comfort, and sustainability. Its generous internal dimensions offer ample space without sacrificing heat retention, although smaller individuals may need to consider fit carefully. The temperature ratings suit typical spring-to-fall camping conditions just above freezing, making it a reliable choice for most three-season outings.

Disclosure: Therm-a-Rest donated a sleeping bag for review.

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