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Castelli Idro Pro 2 jacket review

Castelli's Idro Pro 2 is a Shakedry jacket that’s small and light enough to pack in a jersey pocket but warm enough to get you through a serious storm, with pockets for extra points

Castelli Idro Pro 2
(Image: © Josh Ross)

Our Verdict

Put your hands on the Castelli Idro Pro 2 and you might think it's a typical emergency jacket. Instead, it's more of an all-day jacket that happens to have the option of packing away. It's warmer and more capable than you'd expect and it's also a hard shell with usable pockets


  • - Large easy-to-use zipper
  • - External pockets
  • - Soft interior on the collar


  • - No double action zipper
  • - Minimal stretch means you need to get the fit perfect

When it comes to rain jackets for cycling there's a ton of so-called emergency jackets out there. They are inexpensive, lightweight, and they pack up so small you can bring them along as a just-in-case backup. They are also inherently full of trade-offs. The whole concept is to give up everything you can in service to making the garment lighter and more packable. Then a few years ago a new fabric came on the market and changed everything. 

The fabric is Shakedry from Gore-Tex. Shakedry reduces the layers of a Gore-Tex garment by eliminating any facing layer and allowing the Gore-Tex membrane to stand on its own. Armed with this new fabric technology Castelli has put together something new, the Idro jacket. We've been testing the Castelli Idro Pro 2 jacket - the second iteration of the Idro line. A third also exists, but the Idro Pro 2 is still widely produced. 

You can think of the Castelli Idro Pro 2 as an emergency jacket. It's meant for all-day wear but if the weather changes it's packable and it never feels bulky. Castelli has been able to strip away the trade-offs and make one of the best waterproof cycling jackets out there. 

Castelli Idro Pro 2

At the rear, there's plenty of length to handle road spray (Image credit: Josh Ross)

Design and aesthetics 

The Gore-Tex Shakedry fabric is a finicky bit of technology. Instead of a garment using the fabric to create the design as it's envisioned, the Shakedry fabric has to shape the garment from the beginning. Every piece of the design builds from what is - and isn't - possible with Shakedry. 

This is a black-on-black garment. Colour comes from inks and inks are subject to the same properties as other liquids. Stated simply, trying to get a liquid to stick to a material designed with the sole intention of liquids not being able to stick is difficult. 

In the time that's passed since Shakedry first hit the market, Gore has actually managed to get colour onto the material (in collaboration with British brand, Romance) but it's still rather rare (Rapha has also succeeded). You'll find it used sparingly and not every brand using Shakedry has colours available. Castelli stuck with the original design rather than updated the Idro Pro 2 just to add some extra colour. There are some reflective bits added to combat the black in low-light situations but it's not highly reflective and there's not much of it. This is not a high-visibility jacket. 

The other big design constraint with Shakedry is that it has no stretch. That's a challenge for a technical garment and Gore-Tex has a technology to combat it that Castelli puts to use. Gore-Tex names it simply Gore-Tex stretch technology and you'll find it used all over the Idro Pro 2. The stretchable areas use a cellular structure of compressed fabric: when they stretch, they flatten out. It's technically a little different than what most people expect in a garment but the end result works just as well. You'll find this material over both shoulders and down each side, at the elbows, and at the end of both arms. 

Castelli Idro Pro 2

Shakedry doesn't stretch so it requires stretch panels in strategic areas (Image credit: Josh Ross)

While stretchability and colour are subject to material constraints, that doesn't mean Castelli hasn't been able to use its expertise. There are other Shakedry jackets out there but the Idro Pro 2 is still uniquely Castelli. At the rear you can find the signature, long, drop tail that's a marker of Castelli tops. The silicone gripper sits at the waist but the drop continues lower. Above that drop tail are a pair of pockets that are one of the most compelling reasons to look at this Shakedry instead of others. They aren't big, and there's no stretch, but they represent a unique selling point for the Idro Pro 2.

Keep moving up and you'll see a couple of other classic Castelli design elements. The collar is nice and tall with a lining that's as soft and cosy as your favourite sweatshirt. Closing everything up is a YKK zipper with big plastic teeth. It's not a two-way zipper but it's big and easy to grab. 

Shakedry is more than just a collection of compromises. The idea of tiny holes in the fabric big enough to let water vapour escape while too small to let liquid water in is still the basic mechanism at play. The other part of Gore-Tex technology that most people aren't as familiar with is its hydrophobic nature. There's no need to coat Gore-Tex membranes with a durable water-repellent (DWR) coating because they are inherently water phobic already. That means water beads up and rolls off and it also means that property won't change over time like most DWR. You can wash the Idro Pro 2 and there's no coating to come off. 

These are the basic properties of Gore-Tex but what's changed with Shakedry is a lack of additional layers. The Gore-Tex jacket you are familiar with uses a layer of Gore-Tex material attached to a piece of outer fabric. With Shakedry there's just one layer and that means Castelli gets the Idro Pro 2 down to 158 grams and it's packable in a jersey pocket but it's still warm.

Castelli Idro Pro 2

This nice, soft, neckline is a joy when battling cold weather on a long ride (Image credit: Josh Ross)

Ride experience 

There's a gravel race that happens early in the season not too far from me. This year, Pete Stetina crushed it but I've been there too and I learned a very important lesson in that race. Pockets save races. More succinctly, if you can't reach your food you are going to have a bad day racing 100 miles. The first time I started testing the Castelli Idro Pro 2 it was after failing in that race because of a lack of pockets. 

This jacket is perfect for a long-distance race, or a hard ride with friends in the rain, because it has pockets. There are a variety of amazing jackets on the market that will keep you warm and dry. There are very few jackets on the market that are both hard shell and have external pockets and that's where Castelli comes in. 

There's a couple of things about the Idro Pro 2 that play into what I'm talking about and why I love it. The first thing to understand is that it's substantially warmer than you expect it's going to be. It feels like it's going to be a lightweight shell but it's actually enough of a jacket on its own to handle serious weather. Castelli rates it for temperatures from 6C/43F up to 20C/68F and even though I'm perpetually colder than most, I agree. Pair it with one of the best cycling base layers and you'll be toasty warm without the bulk. 

Not only will it keep you warm but because it's a hard shell it's held up for me through years of use. If you ride through rain and mud, it's a great idea to add one of the best mudguards for road bikes but that won't work for every bike and every situation. It also doesn't completely keep you from getting sprayed with road grime. My softshell jackets tend to come back home with a stripe down the back. They come clean for a while but eventually, they don't. The Idro Pro 2 is a hard shell Shakedry, and as per the name, you can literally shake the water off of it and that includes all the mud and grime that comes with that water. It also doesn’t degrade over time the way other jackets do.

The final piece of this jacket that keeps me coming back to it over and over again is that it has pockets. I'd actually prefer if they were the same, familiar, three-pocket design as most jerseys but I'll take what I can get. Two useable pockets mean I can ditch a jersey and use only a warm baselayer on some rides. It also means easy access to my food when I'm riding hard in a group and don't want to, or can't, stop to get food out. 

While pockets and a hard-shell construction make the Idro Pro 2 special, it does also have to perform as a rain jacket. I find that while it does do better than most hardshell jackets it doesn't completely keep up with sweat. A softshell is always going to perform better in that regard but the Idro Pro 2 is among the best hardshell jackets out there for sweat evacuation. On the other side of that equation, it's 100 per cent successful at keeping the water out. Out of all the times I spent hours in the rain with it I've never once felt like it leaked somewhere. 

Perhaps the most basic part of a jacket is comfort and Castelli has that covered, too. The shoulders have excellent articulation and they don't flap. The sleeves are easy to get on but keep water out and remain comfortable. The pockets I love so much are at just the right height so you don't have to contort your arm to get to them. Probably my favourite comfort feature though is the collar on the Idro Pro 2. It's just the right height and so wonderfully soft.

Castelli Idro Pro 2

Real pockets on hardshell jacket are very rare (Image credit: Josh Ross)


The Castelli Idro Pro 2 is a jacket that will last for years to come. There's no DWR layer to wash off and the hardshell nature means it won't ever end up stained with mud. It's comfortable to wear and way warmer than you think it's going to be while the pockets mean you can reach your food if you are racing or just riding hard with friends. There are other incarnations of Shakedry jackets but Castelli uses its expertise in high-performance cycling clothing to make one of the best.  

Tech Specs: Castelli Idro Pro 2

  • Colour: Black
  • Material: GORE-TEX Shakedry
  • Weight: 158g
  • Size availability: S, M, L, XL, XXL, 3XL
  • Temperature Rating: 6°-20°C / 43°-68°F
  • Price: $400.00 / £360.00 / €350.00 / AU$640.00