10 Best Sleeping Bag Liners 2025 in the United States

The Sea to Summit Reactor Sleeping Bag Liner in Extreme Standard size (85 x 31.5 inches) is designed to add significant warmth—up to 25°F—to your existing sleeping bag, making it a solid choice for winter campers or anyone facing cold conditions. It uses advanced Thermolite Pro fabric, which is lightweight yet insulated, thanks to hollow fibers that reflect body heat back to you. This material also stretches well, allowing good freedom of movement inside mummy-shaped sleeping bags.

The liner's drawcord footbox is a feature that lets you adjust ventilation or snugness at your feet and works seamlessly with certain Sea to Summit sleeping bags. Another practical plus is the HeiQ Fresh odor control treatment, helping the liner stay fresh even after multiple uses, which is advantageous when washing opportunities are limited. Weighing just 0.38 kg, it’s fairly light and compact for backpacking.

While it excels in warmth and hygiene, the price point is higher than simpler liners, and the fixed size may not fit everyone perfectly. Care instructions should be followed to maintain the performance and odor control of the technical fabrics. This liner provides a stretchy, warm, and odor-resistant option that works well in winter and fits mummy bags, with a higher price compared to basic models.

The Friendly Swede Extra Large Sleeping Bag Liner is made from soft microfiber with a cotton-like feel, designed to add about 10°F of warmth to your sleeping bag. Its generous size (44" x 98.5") including a pillow pocket means taller users can stretch out comfortably, making it suitable for most adults. Weighing around 23.5 ounces, it’s fairly lightweight but not ultra-light, so if you need something lighter for backpacking, there’s a polyester version available.

The full-length zipper on the side is a handy feature for easy entry and exit, and the microfiber fabric is durable and machine washable, which makes cleaning straightforward. This liner is versatile for all seasons because it helps wick away moisture in warmer weather while providing extra warmth when it’s cold. It also protects your sleeping bag from dirt, sweat, and bugs, extending its life and hygiene.

While it does add warmth, it’s not a replacement for a thicker sleeping bag in very cold conditions. It is a cozy and practical choice for campers who want a comfortable, easy-to-care-for liner that fits larger users well and works year-round.

The Sea to Summit Reactor Sleeping Bag Liner is designed to add warmth and hygiene to your sleeping bag, making it a solid choice for campers who want extra comfort in cold conditions. Its Thermolite fabric provides good insulation with hollow-core fibers that trap heat effectively, helping keep you warm even below minus 5 degrees Celsius. The liner’s mummy shape and drawcord footbox allow you to adjust warmth and fit around your feet, which is useful for temperature control during chilly nights.

Measuring 85 by 31.5 inches, it fits most adults comfortably without adding much bulk or weight (just under 16 ounces), making it easy to carry on trips. The material is treated with odor control technology, so it stays fresh longer and reduces the need for frequent washing. Fleece and Thermolite typically wash well but can require gentle handling to maintain insulation. While this liner boosts warmth, it is not a replacement for a heavy sleeping bag in extreme cold, and the drawstring closure may take a moment to get used to for a snug fit.

For people camping in cooler weather who want an easy-to-pack, effective liner that improves sleeping bag performance and hygiene, this is a practical option. Its lifetime guarantee from Sea to Summit adds confidence in its durability.