For colder conditions, where you need warmth without excess bulk and weight, the Spark Sp4 Sleeping Bag from Sea to Summit ticks all those boxes and more.
This bag has an expedition mummy bag shape which traps warmth, provides extra space, and also allows for extra layers of clothing. The Spark Sp4 has a comfort temperature rating of -8°C and a lower limit of -15°C so it can be used for expeditions in wintry conditions or climates. This bag has an ultra-light 10D nylon shell and 7D lining which keeps the weight to a minimum. To stop heat loss, the bag has a front neck draft collar and a zipper draft tube and access is easy via the full side zip which also allows you to ventilate if necessary.
For insulation, it’s filled with RDS certified 850 Loft Premium Goose down which has an ULTRA-DRY water-repellent treatment to protect it from moisture. The full box baffle construction helps reduce cold spots and accommodates the extra down in this bag. This sleeping bag also has vertical baffles on the chest to stop the down moving around, and full box baffle construction to reduce cold spots.
For maximum warmth when you’re counting every single gram, the Sp4 Sleeping Bag from Sea to Summit is the ultimate sleeping solution.
-8°C comfort rating, -15°C lower limit
Expedition mummy shape for extra wiggle room
RDS certified 850+ Loft premium goose down
ULTRA-DRY down water-repellent treatment protects from moisture
Light gauge #3 YKK zip
Full side zip with two sliders provides access and ventilation
Vertical baffles on chest prevent down moving during use
Zipper draft tube, hood and front neck draft collar