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The Rab Nimbus is a mid-weight all-purpose synthetic insulated jacket that scored near the bottom of the pack in our ratings. It uses a new type of blown-in synthetic insulation (Cirrus by 3M) that makes it look and feel like a 600-fill down jacket. Unfortunately, the fit of our men’s medium was too restricting under the arms for us to thoroughly field test the jacket. Three people, who fit all 15 other men’s medium jackets well, found it too tight to wear comfortably.

Though we don’t have enough empirical evidence from field testing, we’re hesitant to recommend this jacket solely because of its insulation. We hypothesize the insulation’s short fiber length will be very fragile compared to continuous filament synthetic insulations.Blown-in insulations are primarily intended for fashionable purposes.  We highly doubt this insulation will be durable over the long-term. That makes the jacket a poor value.

We have two complaints about the Nimbus’ design:

  1. Compared to other lightweight jackets, we found the hood fit poorly, both with and without a helmet;
  2. The Nimbus and Rab Xenon X share the same 20-denier fabric. It adds about 2 oz. (57 g) compared to lighter fabrics. We’ve found that most synthetic insulation wears out before the fabric when used for frequent-compression activities like backpacking and climbing. Tough fabrics like the Nimbus’ are best for around town or for working outside.

Features & Specifications

  • 15.3 oz (434 g) in men’s medium;
  • 20-denier 1.3 oz./yd. (44 g/m) exterior fabric;
  • Two handwarmer pockets, one internal zippered pocket;
  • Non-adjustable, not helmet compatible hood.

Description of Field Testing

We tested this jacket on several winter hiking and skiing day trips. Due to the restrictive fit and generally poor performance, we did not want to wear this jacket.

Performance Assessment

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