Fit
The Polartec Powerstretch Pro panels running up the sleeves and down the side of the body not only crank up the breathability, but improve fit by providing stretch. The panels allowed the jacket to reach without us baring our midriff or wrists (nice!). The fitted design layers well over garments, but when slipping your arm into an outer shell, you’ll need to hold onto your cuffs—the Powerstretch panels tend to grab like Velcro. Design quirk: The sleeves are long to allow use of the thumb holes.

Warmth
The Rab Generator Stretch Jacket boosts its mobility with strips of non-insulated, stretchy material along the torso and arms—you will notice the superior breathability at the cost of warmth. Plus, the 60-weight recycled-sourced synthetic insulation just isn’t as warm as other jackets we tested, though it still packs more warmth than a typical fleece jacket or sweater. The synthetic fill retains its insulating properties even when wet.

Compressibility/Weight
Weighing in at one pound, this is far from the lightest jacket in the review. The lighter insulation allows it to pack fairly small, about the size of a large grapefruit.

Features
This is the kind of jacket we will wear all the time for all kinds of activities. It’s a great belay jacket on cool weather climbing trips, ideal for ski touring both in the skin track on cold days and as an extra layer for rest stops and downhills, packs enough warmth to act as your main insulating layer during the summer, and works well for post bike rides and runs whenever it’s chilly. It also comes in a lighter-weight pull over version.

Value
If you consider how versatile this jacket is, the price is hard to beat—it was both the lowest-priced jacket in our test, but was still a very strong performers. The Generator Stretch could replace an expedition-weight fleece and a down jacket on most trips, as breathability and warmth are nearly on par with both.