The Sea to Summit Breeze Lightweight Sleeping Bag Liner Insect Shield is a 288 g mummy-shaped liner in breathable COOLMAX/Tencel fabric, treated with permethrin-based Insect Shield for bug protection built into the fabric rather than relying on separately applied repellent. A stretchy mummy cut and drawcord footbox let it move with you and seal off cold at the feet.
It's designed to be used inside a sleeping bag to add a hygienic layer and a touch of warmth, or on its own in warm, buggy conditions where a full bag would be too hot. The fabric uses recycled materials and is bluesign certified, relevant if environmental sourcing factors into your gear choices; as a liner rather than a standalone insulated bag, it won't add meaningful warmth on a cold night by itself.