The Reactor Midweight enhances your sleep system with advanced Thermolite® Pro fabric. Infrared-absorbing ceramic pigments and hollow-core fibers trap body heat, adding up to 6°C|11°F to a sleep system with minimal bulk. Stretch-knit fabric and arm openings allow unrestricted sleep, making it a great fit for any shape sleeping bag. Quick-drying and easy to clean, it features HeiQ Fresh odor control and helps extend your sleeping bag’s lifespan by reducing wash frequency. Features Boosts Sleep System Warmth – Thermolite® Pro uses Far Infrared technology and hollow-core fibers to trap and reflect body heat without extra bulk 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