Sea to Summit Spark Ultralight Down Sleeping Bag 45°F (Regular) – Lightweight Warmth for Backpacking

Spark 45°F Ultralight Down Sleeping Bag by Sea to Summit (Regular)

Meet the Spark 45°F Ultralight Down Sleeping Bag from Sea to Summit, engineered for warmth on the trail without weighing you down. This technical bag blends high loft down with an ultra-light shell to deliver an impressive warmth-to-weight ratio, making it a strong companion for warm-weather adventures. The insulation uses 850+ fill power down that is responsibly sourced and treated with Ultra-Dry Down, helping it respond to moisture while keeping loft intact through damp nights. It’s designed to compress small in your pack, so you can travel lighter without sacrificing comfort on cool evenings.

The Spark is built with practicality in mind. A contoured mummy shape provides a natural sleeping position, while sewn-through construction keeps weight low. The outer fabric is a 10D nylon shell with a PFC-free DWR finish that adds water resistance without sacrificing breathability. A left side YKK #5 zipper runs along a third of the bag length for snag-free entry and exit, making late-night breaks and early starts smoother. The result is a compact, efficient bag that travels well and settles in as a dependable warm-weather option for hikers, cyclists, and tourers alike.

Materials, performance, and construction

• High loft 850+ fill power down with Ultra-Dry treatment for moisture resistance and loft retention
• Ultralight 10D shell and liner with a PFC-free DWR to improve water resistance while staying breathable
• Contoured mummy shape for a natural sleeping posture and efficient heat retention
• Lightweight sewn-through baffles reduce bulk while maintaining loft and warmth
• Left side YKK #5 zipper provides reliable, snag-free entry

On the trail and packing smart

Two sizes are available: Regular for up to six feet in height and Long for up to six feet six inches, ensuring a comfortable fit for a wide range of hikers. The Spark includes an Ultra-Sil compression sack and a storage cube, aiding packability and organization. Sea to Summit backs its products with a lifetime guarantee against materials or workmanship defects, adding peace of mind for frequent travelers.

• Two size options to fit a range of athletes and sleepers
• Ultra-Sil compression sack and storage cube for compact packing and quick organizing
• RDS certified down with Ultra-Dry treatment for reliable performance in variable conditions
• Lifetime guarantee from Sea to Summit

For best results, allow the bag to loft fully in free air after use and store loosely rather than keeping it tightly compressed for extended periods. While the Spark is optimized for mild nights, its thoughtful construction keeps you comfortable when temperatures dip unexpectedly on shoulder-season trips. This bag isn’t a guarantee of warmth in extreme conditions, but it offers a credible warmth-to-weight balance for those prioritizing packable, reliable performance on the trail.