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Castelli Idro 3 Jacket



Very expensive, but if you have the budget for it, the Idro 3 is a brilliant lightweight waterproof jacket
Brilliant waterproof fabrics
Excellent breathability
Comfortable fit
Slight compromises in packability
138g Recommends

This product has been selected to feature in recommends. That means it's not just scored well, but we think it stands out as special. Go to recommends

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The Castelli Idro 3 is a brilliant lightweight waterproof jacket, using Gore's top line Shakedry technology along with a series of small updates that make it one of the very best for wet weather riding.

When Castelli launched the latest iteration of its Idro jacket as we approached the end of 2021, tech editor Mat Brett covered it in a news story – we'd been suitably impressed back in 2017 when the first version came in for testing, and with a number of updates this time round, it was worth checking out exactly how Castelli proposed to improve on a jacket that had already achieved a 9/10 score.

Those updates amount to a longer cut for improved coverage, a re-jigged forearm construction, a chunkier zip for easier adjustment, and a new fabric (also from Gore) on the lower rear section that's able to stretch – one of the weaknesses of the otherwise awesome Shakedry fabric – while maintaining complete waterproofness.

These updates come together to improve the jacket marginally over its predecessors, keeping it right at the front of the pack when it comes to top-end waterproof jacket performance.

2021 Castelli Idro 3 Jacket - taped seams.jpg

The longer cut, featuring a slightly lengthened body and collar, helps to provide comprehensive coverage that suits me with my longer-than-average body. Much like Gore's brilliant C5 1985 jacket, it is a jacket that can be left on for long periods of time, not feeling restrictive or like it might easily ride up. In heavier rain, it's a real boon to feel that 'extra' protection, while the tall collar helps to reduce unwanted draughts and leaking.

2021 Castelli Idro 3 Jacket - Gore-Tex logo.jpg

The reprofiled forearm cut is also a positive move. Where previously it might have been considered a little tight (in the typical Castelli way where a 'pro' fit naturally means small and narrow), now there's plenty of space for 'normal' sized forearms, which makes it easier to don and strip off when needed, as well as more comfortable on the move.

2021 Castelli Idro 3 Jacket - sleeve detail.jpg

I'm also a fan of the gaiter fitted at the wrist. It's proven useful at keeping the elements out when the heavens have opened, and fits nicely with gloves when the temperature drops. But perhaps most importantly (for me, anyway), it makes the cuff feel so much more comfortable against the skin – in a way, it makes the Idro 3 feel more luxurious than its performance-orientated design might suggest.

2021 Castelli Idro 3 Jacket - cuff.jpg

On the rear, the new waterproof panel helps to deal with one of the Shakedry fabric's real weaknesses – stretchability. There isn't any stretch in Shakedry fabric (making fit and cut even more important from the off), but the new rear panel helps to deal with this, offering stretch in a key area.

2021 Castelli Idro 3 Jacket - rear detail.jpg

Castelli says it's designed for those with full pockets, but I also think it's useful if you happen to be carrying a little extra winter weight around the gut. I certainly am, and in the size large I had on test it makes breathing that little bit easier if you happen to be working hard on a ride.

The panel is attached on three sides, with an overlap flap on the topmost edge. This allows it to stretch effectively, while offering access to your jersey pockets. There aren't any pockets on the Idro 3 itself, but there are on the Idro Pro 3 – the idea being that a pro would put it on and keep it on for the duration a training ride or race.

2021 Castelli Idro 3 Jacket - pocket opening.jpg

Castelli has also done away with the extra ventilation panels that we saw on the first generation jacket, sticking with its decision to drop them on the previous version. The fabric is so exceptional in its breathability that they're really not needed.

The YKK zip is simple to engage and disengage, and pulling it up and down with one hand while riding is easy too.

2021 Castelli Idro 3 Jacket - hem.jpg

However, the downside to the new fabric panel on the rearside and the chunkier zip is that packability has taken a slight hit. Yes, roll it up and it still fits in my Rapha Brevet jersey pocket, for example, but it sticks its nose out of the top of even that relatively spacious pocket.

Essentially, at 138g in a large it remains packable enough for most riders, but if you want something that packs down really, really small, there are options that do that better, such as the Gore C5 1985 Viz.

It's also good to see reflective strips now in place and visible from the rear, boosting visibility in dark light. I don't mind a dark jacket (although a high-visibility option for Shakedry fabric would be welcome in the not-too-distant future), but this adds that little extra safety when you really need it.

2021 Castelli Idro 3 Jacket - rear hem.jpg

I've focused a lot on the parts that have changed from previous generations of the Idro jacket, but overall, the performance remains right up with the very best. Gore's Shakedry fabric is fully waterproof and incredibly breathable (something I've been grateful for through the wet and mild Christmas period), while the quality of the seams and construction is right up there too.

You can wash it with a light detergent easily enough, but often simple rinsing it is enough if all you're trying to do is clean off some dirty road spray. The same also applies to the new fabric back panelling too.


Of course, there's a price to pay. Any jacket sporting Shakedry fabric sits somewhere near the top of the waterproof price tree, but the Idro 3, at a hefty £320, looks down on most.

The Gore Race Shakedry Jacket, for example, also with stretch panels, is £299.99 (we reviewed an earlier version, the C7 Shakedry Stretch, in 2018), as is the C5 Gore-Tex Shakedry 1985 Viz Jacket, which we also reviewed in 2018.

> Buyer’s Guide: 37 of the best waterproof cycling jackets

The only option from Gore that tops the Castelli is the C5 Gore-Tex Shakedry 1985 Insulated Jacket which, as the name suggests, has some added insulation for £329.99.

Perhaps unsurprisingly, Gore seems to offer slightly better value for similar jackets, given that it owns the main fabric technology. However, Rapha's Pro Team Lightweight Gore-Tex Jacket is still available for £220, which in the battle of premium cycling brand names (featuring Shakedry tech) is a compelling price tag versus the Idro 3.


Although very expensive, there are precious few jackets out there that can match the sheer performance of the Castelli Idro 3. With sensible design tweaks, it remains one of the best waterproofs out there.


Very expensive, but if you have the budget for it, the Idro 3 is a brilliant lightweight waterproof jacket

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Make and model: Castelli Idro 3 Jacket

Size tested: Large

Tell us what the jacket is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Castelli says: "This jacket is a game changer. To call it a rain jacket is only touching the surface. While it's an outstanding rain jacket, we end up using it 95% of the time in dry conditions because it's so compact that we always have it in our centre pocket, ready to put on for a long, cold descent, or to cover up at a coffee stop, or to keep some heat in while waiting for the other guys to show up for the ride. We named this jacket Idro 3, which at first doesn't say much, but let's break it down. |Idro is Italian for hydro, meaning having to do with water. Or in this case, keeping water from coming in while letting sweat escape. It does both very, very well. Best we've ever made. The 3 in the name indicates this is the third iteration of this product, and we're nearing the maximum of what's possible with a shell jacket. There's a big innovation on the back, with a large high-stretch GORE-TEX® panel that allows us to give the jacket a trim fit (i.e., no flapping fabric, so you can just ride away from your riding companions), yet the jacket expands to fit around loaded pockets '' or to fit normal people with a bit of a gut. Beyond the stretch panel, we've carefully refined the fit, the finishing construction, the large reflective panels, and especially the wrist closures with a new internal gaiter. We've made this jacket to be as fully featured as possible when you wear it, but it will spend a lot of time in a pocket on those days when it might rain or when you just need it to cover up on long alpine descents. It weighs less than many jerseys and stashes away to occupy only half a jersey pocket. There is one drawback: the fabric is so lightweight that it is a little bit fragile, so treat it with care. It'll be one of the most important pieces in your cycling wardrobe."

Tell us some more about the technical aspects of the jacket?

Castelli lists:

- The lightest and most packable fully waterproof Castelli GORE-TEX® jacket

- GORE-TEX® SHAKEDRY™ product technology sheds water yet offers unmatched breathability

- The entire lower back is in GORE-TEX® Topo stretch fabric to expand in diameter if you have a few extra winter kilos or full pockets

- Reflective tape on back of both sleeves for high visibility in low-light conditions

- YKK® Vislon® waterproof zipper slides easily for ventilation adjustments

- Internal wrist gaiter seals wrist and integrates with glove to keep water out

Rate the jacket for quality of construction:

Practically faultless, all seams and joins are perfect.

Rate the jacket for performance:

About as good as it gets when it comes to waterproofness and breathability.

Rate the jacket for durability:

Shakedry isn't as hardy as three-layer fabrics, but look after it and it should be fine.

Rate the jacket for waterproofing based on the manufacturer's rating:

As good as it gets.

Rate the jacket for breathability based on the manufacturer's rating:

Castelli gives it a 3/5 for breathability on its own scale, but the fabric is so good that zippered vents really aren't necessary in my opinion.

Rate the jacket for fit:

A great, slim fit with the added benefit of the stretchier panel on the rear.

Rate the jacket for sizing:

Castelli typically sizes smaller than most (so if you're normally a size L like me, you'd usually be advised to buy an XL), but here I fit into this size L snugly with no real restrictions, suggesting to me that the sizing is generous (for Castelli). I wouldn't want to wear too many layers underneath it though.

Rate the jacket for weight:

You don't notice the 138g in your pocket, just the folded size.

Rate the jacket for comfort:

Impressive comfort for what in many places is a high-tech shell. The cuffs and body length make a real difference here.

Rate the jacket for value:

At £320, the Idro 3 costs more than its main rivals. It's almost painfully expensive, though the performance and overall experience go a long way to justifying it.

How easy is the jacket to care for? How did it respond to being washed?

You need to take care here, but a light detergent or simple rinse is enough to keep it well cared for. Follow instructions!

Tell us how the jacket performed overall when used for its designed purpose

Brilliantly, first class.

Tell us what you particularly liked about the jacket

Brilliant waterproof fabrics, excellent breathability, comfortable fit.

Tell us what you particularly disliked about the jacket

Expensive, slight compromises in packability.

How does the price compare to that of similar products in the market including ones recently tested on

It's expensive even compared with other Shakedry jackets. The Gore Race Shakedry Jacket, for example, also with stretch panels, is £299.99, as is the C5 Gore-Tex Shakedry 1985 Viz Jacket. The only option from Gore that tops the Castelli is the C5 Gore-Tex Shakedry 1985 Insulated Jacket which, as the name suggests, has some added insulation for £329.99.

Perhaps unsurprisingly, Gore seems to offer slightly better value for similar jackets, given that it owns the main fabric technology. However, Rapha's Pro Team Lightweight Gore-Tex Jacket is still available for £220, which in the battle of premium cycling brand names (featuring Shakedry tech) is a compelling price tag versus the Idro 3.

Did you enjoy using the jacket? Yes

Would you consider buying the jacket? Yes, though I'm not sure I'd spend this amount of money when the likes of the Rapha Pro Team Lightweight Gore-Tex Jacket exist for £100 less.

Would you recommend the jacket to a friend? Yes, I'd have to based on its performance, if I knew their budget could stretch to it.

Use this box to explain your overall score

A first class waterproof jacket. It'll be too expensive for many, but if you have the budget for it then it'll be a brilliant investment.

Overall rating: 9/10

About the tester

Age: 30  Height: 188cm  Weight: 80kg

I usually ride:   My best bike is:

I've been riding for:   I ride:   I would class myself as:

I regularly do the following types of riding:

Add new comment


fenix | 1451 posts | 1 year ago

What happened to the printed shakedry that came out a few years back ? I thought that was the only way to get colour shakedry ?

I'd settle for a patch of fluo over the back pockets and on the arms though - you prob don't even need it to be breathable for just some visibility spots. 

Chris Hayes replied to fenix | 1216 posts | 1 year ago

I thought that Rapha were going to release a coloured version (like a tie-dye)....must have missed it...

Global Nomad | 328 posts | 1 year ago

would be good to know from earlier owners if their shakedry jackets are still performing after 3+ years....that might make the maths more compelling...

cyclefaster replied to Global Nomad | 106 posts | 1 year ago
1 like
Global Nomad wrote:

would be good to know from earlier owners if their shakedry jackets are still performing after 3+ years....that might make the maths more compelling...

I've had my shakedry and about 3 years and it's been faultless. It's not something I wear every ride, but I'm always grateful for it when needed, even as an extra layer on dry but colder days. It's so light you don't really feel you're wearing it. I just wish it didn't look like I was wearing a bin bag.

Rapha Nadal replied to Global Nomad | 1454 posts | 1 year ago

Not quite 3 years yet but it still performs as well as the day i bough it. It even has the longer fit & stretch panels featured with this Castelli jacket but cost a lot less! 

dodgy replied to Global Nomad | 304 posts | 1 year ago

I'm a Shakedry owner, it's literally the only cycling related product I own that was marketed as 'waterproof' and lived up to the claim!

Looking at you sealskinz....


Chris Hayes replied to dodgy | 1216 posts | 1 year ago

You can look at my Assos too and my Sturmprinz which after a couple of seasons has lost its waterproof capabilities.... I tried to coat it with Nikwax but so far it hasn't made any difference.

emjay49 replied to Global Nomad | 57 posts | 1 year ago

Bought mine a good few years ago just after they first came out. In the past 12 months it has started to wet out in a few areas when in heavy persistent rain. Perfectly OK for showers and intermittent weather. Also really versatile to stuff in the back pocket when in changeable conditions or even when up on high and need a bit of protection. Would definitely recommend and I will replace this one with another when it's finally given up.

fenix replied to Global Nomad | 1451 posts | 1 year ago

Yes  - still flawless.  Like others though - I don't use it every ride - it is just for heavy rain for me - anything light and I don't bother with it. 

If I were you - look for a cheaper early version and get one big enough to wear over your winter kit. Look after it and it will be perfect for years.

It is paper thin so I never wear a bag over it or wear it offroad etc.

agp replied to Global Nomad | 11 posts | 1 year ago

Original Idro owner (~3 years) - don't use often but when you need it there is nothing comparable - was very helpful for Festive 500 this year! ShakeDry is only cycling item I specifically recommend. I got mine for an end-of-line discount, so that retail price does sting ...

BUT it is not miraculous! Although very breathable, if you work hard, you will heat up and may still sweat. In UK winter when raining, wearing with a LS base layer and a SS jersey is usually enough.

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