Will Renwick gives his take on the synthetic insulated jacket by British brand Rab

This mid-price synthetic jacket (available in both men’s and women’s versions) has done its best to imitate a down one – and the result is convincing.

First of all it looks very much like a down-filled garment, thanks to the narrow baffles that structure the loose Cirrus fibres. Secondly, and more importantly, it feels a lot like a down fill – the Cirrus is light and lofty, rather than having that sponginess often associated with synthetics.

And what about the warmth to weight? It’s not too far off down in this regard either. A size Large weighs 580g and provides about as much warmth as 600 fill-power jacket, which can weigh around 450g. I found it warm enough for a late autumn overnight in Scotland. For winter mountains I’d say you’d still want a few layers underneath as well.

One of the advantages of synthetic insulators is in their effectiveness while wet (water-resistant down is now available, but can be expensive). The Nebula has some water resistance thanks to its Pertex Endurance outer fabric, but when this is overwhelmed it will still offer good insulation. I managed to get the sleeves damp while taking down a very sodden tent and found that the synthetic fill still performed effectively, and it didn’t take too long to dry in light wind either.

It’s very handy that the Nebula will stuff into its own pocket (left handwarmer), however, the finished result is quite bulky – about the same size as loaf of bread. So it does take up quite a bit of room in a pack. I’d say this is one of the main drawbacks to choosing this jacket over a down one.

Other features worth mentioning include the large chest pocket, oversized handwarmer pockets and a shape-able peak on the hood – which can fit a climbing helmet. Finally, the cut is quite large. I’m usually a Medium but I think I would have been better off with a Small.

Review: March 2016