Castelli Idro 2 jacket

Complete weather protection in a tiny package




  • Weather protection
  • Fit
  • Packability
  • Breathability


  • Nothing

Price as reviewed:


As testing environments go, completing LEJOG during the wettest week of the year, was probably the perfect time to test the latest Castelli Idro 2 waterproof jacket. And fortunately I can say that it came away from the test with flying colours.

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The Idro 2 is constructed of Gore-Tex’s genius Shakedry two-layer material to provide complete wet weather protection. Shakedry does exactly as it says, the outer layer is effectively the waterproof membrane so there is no material for water to soak into as you can get with a three layer fabric that traditionally puts the waterproof layer in the middle of the jacket.

A quick flick of the wrist and the jacket expels any water hanging on to it, leaving it dry enough to comfortably stow in your pocket. It also boasts an impressively high level of breathability as you would expect from Gore-Tex. On some days in testing I experienced up to ten hours of constant rainfall and it’s testament to the function of the Shakedry fabric that it never wetted out plus I never really experienced the classic boil-in-the-bag feeling associated with a lot of waterproofs.

Watch: How to get the most out of bad weather riding

The Idro 2 is minimalist to the extreme, there are no pockets, fancy linings or even any forms of adjustment apart from the easy to use YKK zip. What this does mean though is this thing is tiny. It packs down smaller than many ‘windproof’ jackets and weighs a scant 109 grams in the medium size I use. Such is this small size that I had to question how protective it could be. I needn’t have worried. It does have a tall collar and tight cuffs that prevented water ingress as well as any other jacket I have used.

Buy now: Castelli Idro 2 jacket from Tredz from £208

The fit is definitely ‘race cut’ and if you want to use the Idro 2 as your winter waterproof it might be worth going up a size. However it is such a high performing jacket with excellent breathability that you can get away with wearing one less layer and still retain the same amount of weather proofing as a thicker jacket. If you do want a similar jacket with more features and a little more winter practicality Castelli produce the Idro Pro 2 jacket. This has pockets and some other differences to make it a little more versatile.


Superlative performance in a tiny package. There's nothing not to like about the Castelli Idro 2 jacket, great fit and almost perfect on the bike performance. There are few to beat it.


Colours: Black/red
Sizes: S-XXXL
Weight: 109 grams (size medium)