Adding a liner to your sleeping bag boosts warmth, comfort, and cleanliness on your camping trips. Liners create a soft, cozy barrier between you and your bag, helping regulate temperature and keeping the interior clean by reducing direct contact with sweat and dirt. They're easy to wash, which means less frequent cleaning for your sleeping bag, ultimately extending its lifespan. Plus, they can be used on their own in warmer weather for lightweight versatility. 4900027 PolyCotton/Charcoal 4900029 Brushed Polyester/Charcoal