Lightweight synthetic 3-season trekking sleeping bag: actual weight, volume, and conditions
The Naturehike MG120 trekking sleeping bag weighs 670 g in size M with compressed dimensions of 18×15×30 cm — dimensions suitable for multi-day backpacking. The comfort temperature is +5°C, measured according to the GB/T 38426-2019 and ISO 23537 standards using a thermal mannequin, insulated mat, and long underwear. In field conditions without this equipment, allow for a margin of 3 to 5°C. The mummy cut features an opening at the feet allowing you to move around without leaving the bag — useful at camp during morning preparations. The YKK zipper is accessible from the inside.
SUNDOUCE Gold synthetic insulation: advantages in damp conditions
The SUNDOUCE Gold 60 g/m² double-layer insulation is made of synthetic microfilaments that retain their insulating properties when damp—unlike natural down, which loses a significant portion of its effectiveness when wet. This is a practical advantage for trekking: condensation in the tent, morning dew, or ambient humidity at altitude. The stated insulating power is 5.29 CLO with a bacterial inhibition rate of over 90% maintained after machine washing. The GRS-certified 20D nylon outer fabric incorporates a fluorine-free water-repellent treatment. Note regarding the weight/insulation ratio: for an equivalent thermal range, 700-800 cuin down insulation would weigh less than 500 g—the synthetic fill here represents a trade-off in favor of moisture tolerance and simplified maintenance, at the expense of weight.
Foot opening and zip accessible from the inside
A dedicated foot opening allows you to take your legs out without unpacking the whole bag, useful for short trips around the bivouac (cooking, washrooms) without losing the heat accumulated in this trekking sleeping bag. The main zipper remains accessible from the inside, which makes adjustments easy without having to take an arm out of the bag.
GB 18401-2010 Class A certification
The fabric of the MG120 is certified GB 18401-2010 Class A, the strictest level of this Chinese textile safety standard, normally reserved for products in direct and prolonged contact with the skin of infants. Applied here, this classification documents the absence of harmful substances exceeding regulatory thresholds on the outer fabric of this lightweight sleeping bag.
For itineraries in dry conditions where weight is a priority, the Aegismax Leto offers +7°C comfort at 642 g with 700 fill power down insulation.
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The field guide helps you choose based on skill level, temperature, needs, and weight. Support answers specific questions.
Find my bag Contact supportFrequently Asked Questions
The Naturehike MG120 has a comfort temperature of 5°C and a lower limit temperature of 0°C, measured to the ISO 23537 / GB/T 38426-2019 standard. These values apply under standard conditions: sleeper in thermal base layers, on an insulated sleeping mat. It is designed for Trekking, bivouacking use (3 seasons).
The Naturehike MG120 is filled with Synthetic. Synthetic insulation keeps insulating when damp, dries quickly and needs no special care — suited to changeable conditions or family trips. The Naturehike MG120 weighs 670 g, which places it in the ultralight category.
A 3-season sleeping bag is designed for spring, summer and autumn. Its comfort temperature sits between 0°C and +5°C, which covers most wild camps in France up to 2,500 m outside winter conditions. In winter or above 2,500 m, a dedicated cold-weather bag is needed.
A 3-season bag is suited to night-time temperatures between roughly 0°C and +15°C. Below 0°C, thermal comfort is no longer assured without extra equipment (liner, additional sleepwear). Above +15°C, most sleepers will find the bag too warm: venting through the foot zip helps regulate.
For the vast majority of walkers and trekkers in France (GR20, GR5, Tour du Mont Blanc from June to September), a 3-season bag with a 0°C comfort rating is sufficient. A 4-season bag is only needed above 3,000 m outside summer, in winter conditions, or for exposed high-altitude wild camps in autumn.