A synthetic sleeping bag with exceptional warmth-to-weight ratio

Synthetic sleeping bags designed for cold weather usually have a double-layer construction with offset seams so that the sewn-through stitching in each layer that holds the insulation in place doesn’t let cold air in. This is a thermally efficient construction but also a heavy one as it involves two extra layers of material plus twice as much stitching. Mountain Hardwear has come up with a much lighter construction method that welds the insulation to the shell and the lining, eliminating stitched seams so only one layer is needed. This results in a bag described as ‘the highest performance synthetic bag on the market’ that is ‘engineered to be the lightest and warmest synthetic bag available’. Certainly for a synthetic bag it is very light for the warmth. For me it’s fine down to -5°C.

The design is good too. I like the centre zip for ease of entry and exit and for sitting up. It would be nice if it was a little longer though. The baffle behind the zip has Velcro dots to keep it closed. The wide draft collar also closes with Velcro. The hood has a filled tube round the edge that is warm and comfortable. The fit is quite snug – this is a bag to turn over with rather than in. I could wear a light down jacket inside if necessary. The shell and fill are soft and comfortable.

This is the lightest, lowest bulk and most expensive synthetic bag reviewed. It’s also the best and should be okay in temperatures down to -6°C unless you’re a cold sleeper. Below that insulated clothing or a light outer bag would probably be needed.