Sea to Summit Hamelin Synthetic Sleeping Bag

The Sea to Summit Hamelin is a synthetic-fill sleeping bag weighing 1124 g total, built with recycled Revive Loft insulation and a semi-rectangular, contoured shape that gives more room to move than a mummy cut while still tapering enough to trap warmth. A draft collar around the shoulders and draft tubes along the zipper stop warm air escaping through the usual weak points of a bag with an opening. The full-length two-way zipper can be opened from either end for ventilation on a warm night or for feet to poke out, and the whole bag is bluesign-certified, meaning the materials and dyeing process meet a recognised environmental and safety standard. Synthetic insulation means it keeps some warmth even if it gets damp, unlike down, and is easier to care for and dry in the field - the tradeoff against a down bag of similar warmth is more bulk and weight to carry. No temperature rating is listed here, so pair the weight and semi-rectangular shape with the season you're using it in rather than assuming a specific comfort limit.