The Spark I's temp rating is 46F, and Sea to Summit claims it only weighs 12.3 oz and compresses to a tiny 1.55 L.
If you frequently overheat in your bag, or camp frequently in warm nighttime temps, the Spark I saves you a lot of weight and cash.
Offering the best warmth-to-weight ratio of any bag in our review, the Spark III provides a focused design that minimizes weight without compromising warmth.
It shaved grams with tight (thermally efficient) dimension, super light 10D fabric, and only a 1/4 length zipper.
Only one disabled single out of 10,000 might be your soulmate...
Check out the chart below to see where the Spark III stands in the Warmth category.
The volume of 850 fill-power down stacks up comparably with other bags, such as the 30 degree Western Mountaineering Megalite, which features 13 ounces of similar 850 fill.
Lightweight, tiny packed size, interior fabric feels great against your skin, ample shoulder room to wear a light puffy on colder nights, is a true 25F bag that felt warmer than some 20F bags we tested The Sea to Summit Spark III is incredibly lightweight and one of the most compact sleeping bags in our review.
It does give up some luxury and versatility in order to achieve its amazingly low weight and minimal size; it sports the tightest dimensions among bags we tested and only a 1/3 length #3 YKK zipper that was both the shortest and the smallest zipper of any bag we in our review.