Therm-a-Rest Boost 650 20F/-6C Regular

Comfort is not one-size-fits-all, which is why the shape of the Boost 650 can be customised to find the perfect balance between freedom of movement and warmth. As a spacious, semi-rectangular sleeping bag, the Boost offers the space you need for side sleeping, turning over, stretching out and relaxing. The semi-rectangular shape offers much more space inside than a mummy sleeping bag - you feel free and can sleep in any position you want all night long. But more space requires more body heat to keep the body warm. This is where the WarmZip comes in. The raised zip transforms the shape of the Boost 650 from a semi-rectangular sleeping bag into a thermally efficient mummy sleeping bag. This distributes the down around the body and reduces the space that the body needs for warmth. With the WarmZip, the heat output of the Boost can be increased by up to 6 °C