The Rab Nucleus is made with a "Thermic" stretch fleece. Rab calls it a mid-weight fleece, but it feels more like a lightweight option. It's light, breathable, and will get you from your car, high into the mountains without a problem. It's a great option if you're looking for a technical fleece that is inexpensive relative to the competition.
Performance Comparison
Out for a pre-dawn mission in the Nucleus Hoody. This layer kept us warm when hiking fast on a cold start, and it's highly breathable. The pockets are a nice option for keeping your hands warm as well.
Photo: Cam McKenzie Ring
Warmth
The Nucleus sacrifices warmth for breathability and easy layering. It's one of the thinnest pieces in our test group, and it's made for moving fast in the mountains and not hanging out at camp in cold weather. This is not necessarily a bad thing, as we often need something that will keep us warm on cool days without overheating our bodies.
This fleece is on the thin side and not as warm as many of the other models that we tested. The hood helps retain warmth, and it fits nicely under a helmet, but it doesn't have the same full face gaiter that the Patagonia R1 and Arc'teryx Fortrez Hoody have.
Photo: Cam McKenzie Ring
Comfort
The Nucleus is a fairly comfortable layer for several reasons. The interior gridded fleece is soft, and it feels nice against your bare skin — not scratchy at all! The hood is form-fitting but not too tight, and the cut is tapered but not too constricting. We like that the hood fits easily underneath a helmet. It's not quite as plush as other hi-loft models, but we don't mind wearing it all day long. It also features two handwarmer pockets that you can access with a backpack or harness on.
Hand pockets are a nice touch and add to the overall coziness and comfort of a fleece jacket.
Photo: Cam McKenzie Ring
Breathability
This jacket is highly breathable thanks to the gridded fleece. It feels on par with other technical fleeces that are featured as top picks and award winners in this review. We took it hiking, climbing, and running, and it performed well in all seasons, thanks to its fantastic thermoregulation. The fabric features Grid technology that allows moisture to easily vent from the cracks between the islands of insulation. This, in addition to the pockets, offers some level of ventilation, making it a perfect pick for aerobic sports.
This model uses the same grid technique as the Polartec Power Grid fleeces. The channels offer a thin layer for your moisture to escape.
Photo: Cam McKenzie Ring
Layering Ability & Ease of Movement
The Nucleus is super easy to layer. It works over a thin underlayer, like a sweat-wicking t-shirt or tank top, and then it also layers well under a thicker soft-shell jacket or a windbreaker jacket. The material is stretchy, and there is ample room in the shoulders for climbing or other active pursuits. The full-length zipper is not our favorite option for wearing under a pack or harness, as it can cause pressure points, but the length is long enough so that it doesn't ride up.
We could layer just about every which way with this model. Over a base layer, under a heavier jacket, with a harness, with a backpack, etc, etc. Our only quibble is that a full-length zipper isn't always the most comfortable option when paired with a waist belt.
Photo: Sanni McCandless
Weather Resistance
Fleece jackets are not known for their weather resistance, and this one scored about how you might expect a thin fleece would — not very well! Water absorbs straight into the material, and the wind rips right through it.
The exterior of this fleece offers no protection from the elements. Water soaks right in and it doesn't block the wind at all.
Photo: Cam McKenzie Ring
Value
This jacket retails for less than our Editors Choice, making it an attractive pick for the price.
Conclusion
The Rab Nucleus is a lightweight technical fleece that stands out for its great breathability and features. Consider it as a low-priced technical fleece that'll perform for all winter, fall, and spring days. Even wear it on cooler nights in the Summer.
This jacket is fairly plain, which we don't mind. It doesn't look too technical or "muppet-like," and it comes in some nice color choices.
Photo: Scott Ring
