Blue Sleeping Bag Liners

For hot, humid conditions pick thin, sweat-wicking fabrics like Tencel, bamboo, or CoolMax that breathe and dry quickly. Lightweight silk liners such as the 5 oz Sea to Summit Stretch Silk can work for travel, but moisture-wicking synthetics generally feel cooler on sticky nights.

You can expect different boosts depending on material: silk liners add around 9.5°F, fleece models typically add up to 12°F, and insulated options can add as much as 25°F. Models like the Bundle Monster microfiber fleece two-pack are rated to about a 55°F baseline and commonly add roughly 10°F of warmth.

Mummy-shaped liners match tapered bags with a snug hood and footbox, making them better for backpacking and cold-weather use. Rectangular liners offer more room for restless sleepers and double as travel sheets for hotels or bug-prone hostels; lightweight silk options at around 5 oz also pack down very small for backcountry trips.

Match the liner length—regular, long, or women's—to your bag and check girth so the liner isn't too tight or loose inside the shell. Some synthetics like CoolMax provide stretch for a closer fit, and mummy geometries use hoods and tapered footboxes to conform to tapered sleeping bags efficiently.

Insulated liners such as Thermolite use hollow-core fibers and can boost warmth by as much as 25°F while drying about 50% faster than cotton. They work well for winter car camping, van life, or RVing when you want extra insulation without carrying a significantly heavier sleeping bag.