Backpacking: A mummy-shaped liner can add 5° to 15°F of warmth to your bag. It also helps your bag last longer by protecting it from dirt and body oils.
Traveling: A rectangular liner separates you from unclean bedding.
Liner materials
Silk: Very light, compact and insulates in cold weather. Absorbent and breathable in warm weather. Price: moderate to expensive.
Cotton: Strong, durable, absorbent. Not the lightest or most compact. Price: economical.
Fleece and microfleece: Warmer, heavier, soft, moisture-wicking, quick-drying. Mid- and heavyweight varieties are bulky. Price: moderate.
