Boost your sleep system’s warmth with the Reactor Fleeceweight. Thermolite® hollow-core fibers and grid fleece trap and reflect body heat, adding up to 8°C|14°F with minimal weight. The stretch fleece and arm openings allow freedom of movement, while snap attachments fit Sea to Summit sleeping bags for easy access. Easy to clean and quick-drying, it features HeiQ Fresh odor control. Using a liner reduces sleeping bag washes, helping preserve loft and extend lifespan. Features Boosts Sleep System Warmth – Reactor Fleeceweight uses Thermolite® hollow-core fibers and grid fleece to trap warmth with minimal added weight Freedom to Move – Stretch-knit and shaped arm openings allow unrestricted movement, providing natural comfort throughout your sleep Technical Shape and Hood – Ergonomic design with a fitted hood delivers optimal warmth and comfort without extra weight or bulk Stay Fresh Longer – HeiQ Fresh odor control technology keeps the liner fresh after extended use Sleep System Integration – Snap connectors at the shoulders easily pair with Sea to Summit sleeping bags for quick, hassle-free entry and exit Easy to Keep Clean – Machine washable construction simplifies care and reduces wear on your sleeping bag over time Lower Impact Materials – Crafted with certified recycled fibers and bluesign APPROVED materials to minimize environmental impact Can be used on its own as a lightweight sleeping bag in warm-weather conditions