Compressibility
Rab’s Eco 3D insulation is very lofty and warm, but lacks the ability to really be compressed. When spread out, the Genesis 3 is a big, fluffy bag and when stuffed, it’s a big tight bundle. If you have room in your pack, is a great product for cold nights in the backcountry though.

Warmth to Weight ratio
Though the Genesis 3 runs heavy at 4.25 pounds (our scales), it also runs warm – the warmest in its class. We all felt warm and snug during 20ºF nights, even when camping on snow! That helps salvage what otherwise would be an abysmal warmth-to-weight ratio. It’s not the best in the class, but its respectable. 

Comfort
The cut of the Genesis finds that fine line between warm and roominess and follows precisely follows it. From the ample, yet snug hood to the spacious but toaster-oven-like warmth of the footbox, the bag’s cut and fit maximizes warmth by minimizing excessive dead space. At the same time, even I – with my 48-inch chest and 36-inch waist – found I could wriggle and turn through a variety of positions during the night without any lose of comfort or feelings of constriction. The two-slide zipper proved essential for comfort in warmer conditions as it allowed independent venting of the legs and feet while keeping the upper bag closed up tight. 

Durability 
The tough but light Pertex lining and ripstop shell, as well as the Eco 3D insulation are made from 100-percent recycled polyester – and the entire bag can be recycled itself once its useful life is over. Even though it was this material’s second time around the block, it proved quite durable. The ripstop polyester shell, as well as the lining, boasts a remarkably soft feel but it proved puncture and snag resistant. The insulation, meanwhile, plumps up nicely when unstuffed and we didn’t find any loss of loft during the extended test period.

EN Comfort limit = 30ºF / -1.5ºC
EN Lower Limit = 19ºF / -7.5ºC