10 Best Sleeping Bag Liner For Warmth 2025 in the United States

The Friendly Swede Sleeping Bag Liner is a versatile accessory for camping and hiking in various weather conditions. Made of microfiber, it provides a cotton-soft feel while being durable and machine-washable, making it easy to maintain. This liner is designed to add up to 10°F to your sleeping bag, which is beneficial during cold nights, while its moisture-wicking properties keep you comfortable in warmer conditions.

The full-length zipper adds convenience and allows for easy entry and exit. With generous dimensions of 41” x 86”, it offers ample space, even for tall users, and includes a pillow pocket for added comfort. Weighing just 17.6 ounces, it is lightweight and easy to carry in its stuff sack, making it ideal for travel and outdoor adventures.

Some users may find the zipper less durable over time. Additionally, although it protects against sweat and bacteria, it might not completely prevent bed bugs in hostel environments. Despite these minor drawbacks, its lifetime warranty makes it a reliable choice for enhancing sleeping comfort during camping trips.

The Sea to Summit Reactor Sleeping Bag Liner in Fleece Standard (85 x 31.5) is designed to add extra warmth and maintain personal hygiene when used inside a sleeping bag. The liner utilizes hollow-core Thermolite EcoMade fibers in a grid-pattern fleece to maximize heat retention, making it a good choice for those looking to enhance their sleeping bag's warmth.

The mummy shape, complete with shoulder zippers and a footbox drawcord, enhances thermal efficiency and allows for easy temperature regulation. Additionally, the drawcord footbox can be opened or closed for comfort and integrates well with Sea to Summit's Free-Flow Zip system on certain sleeping bags. This liner also features HeiQ Fresh odor control technology, which helps keep it fresh even after prolonged use.

Weighing around 451.9 grams and measuring 85 x 31.5 inches, it provides ample space and warmth without being overly bulky. The liner is also easy to care for, thanks to the durable Thermolite material. While it might not be suitable for those who require a liner for extreme cold conditions, it offers a good balance of warmth, comfort, and hygiene, making it a solid choice for campers and outdoor enthusiasts.

The Sea to Summit Reactor Sleeping Bag Liner in Fleece Compact is designed to enhance the warmth and hygiene of any sleeping bag, making it a valuable addition for camping, hiking, and backpacking enthusiasts. Made from hollow-core Thermolite EcoMade fibers in a grid-pattern fleece, it efficiently retains heat, which is ideal for three-season use with a temperature rating of 32F and above.

The liner features a mummy shape for maximum thermal efficiency, shoulder zippers, and a drawcord footbox that can be opened or closed for personalized comfort. Additionally, the HeiQ Fresh odor control technology ensures the liner stays fresh even after extended use, which is a great plus for long trips. It is also compact and lightweight, weighing just 0.92 pounds and measuring 78 x 31.5 inches, making it easy to pack and carry.

However, while the thermal boost and odor control are beneficial, some users may find the polyester material less breathable compared to natural fibers. Also, its dark blue or black color options are limited. The product is backed by the Sea to Summit Guarantee, adding a layer of reliability. This sleeping bag liner is best suited for adults who need extra warmth and hygiene on their outdoor adventures.