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Castelli Idro Jacket - Men's

Sale $262.46 $349.95 25% off

Item # CST00GZ

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  • Black, L ($262.46)
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Item # CST00GZ

The best and lightest.

Over the past five years, Castelli has made a name for itself by continuously redefining what we expect from race-worthy, breathable weather protection. The Gabba, the Tempesta, the Perfetto—these names have come to define the genre. The Idro Men's Jacket is this heritage's latest addition; it's also possibly the most impressive. It's the result of a partnership with W.L. Gore and Associates, and—with Castelli proudly proclaiming it the lightest Gore-Tex jacket in the world—the Idro combines the best and lightest features from across the Italian brand's line.

The jacket's key construction element is Shakedry, a breathable membrane that enjoys the water- and windproof qualities that made Gore-Tex a legend in the general outdoor industry. It'll block the wind like your Gabba, but it's also literally waterproof, so heavy, prolonged rain that exposes the Gabba as merely water-repellent doesn't penetrate the Idro. This is backed up by the "GUARANTEED TO KEEP YOU DRY" policy, a promise that Gore-Tex rolls out in CapsLock for its official literature.

Considering the enormity of that statement, we've opted to preserve Gore-Tex's jarring textual choice in our own copy—especially since the Idro pairs that huge claim with a correspondingly tiny one: it only weighs a claimed 123g for a size large. This low weight is possible because Shakedry eliminates the usual face fabric, so it's a two-layer membrane that preserves an uncompromising balance of breathability and protection while reducing bulk to expand Gore-tex's appeal to include elite cyclists.

Castelli's penchant for very targeted innovation means that navigating its catalogue can occasionally be as tricky as negotiating damp corners on rainy descents. For comparison's sake, we'd situate the Idro as an ideal blend of two of Castelli's leading anti-weather tops: the Riparo Rain Jacket and the Tempesta Race Jacket.

The Riparo is a few grams lighter than the Idro, but it's also far less breathable. Castelli's Tempesta Race Jacket, on the other hand, is as breathable as the Idro, but it's also almost 80g heavier—that's almost 70% more weight. If this jacket were intended for nothing but leisurely noodles, then we'd have no problem with those added grams or the risk of internal moisture accumulation during hard efforts. But it's not for leisure; it's for racing. It's for days when you can't afford to let Mother Nature's springtime tantrums keep you from the start line, impede intervals, or force you to load down your bikepacking panniers with yet more heavyweight gear.

That stowability is arguably even more desirable for race situations than bikepacking, though. The Idro's ability to pack down to less volume than a pair of knit gloves (about half a pocket by Castelli's estimate) means it will actually stow in the minimalist pockets on race jerseys—a claim that neither the Tempesta nor the Riparo can make.

While it's not being stowed in those pockets, the Idro features zippered access to them, ensuring protection doesn't mean you're bereft of ride essentials. The front zipper is a waterproof YKK Vislon model, and it works with the anatomically shaped wrists and seam taping to ensure there are no coverage gaps or points of watery ingress to compromise the jacket's CapsLock guarantee. The seam taping is also reflective, which is another small detail that will help ensure your ride goes according to plan.

  • A cycling jacket for rainy, windy racing and training
  • Gore-Tex Shakedry membrane protects and breathes
  • Water- and windproof protection in a race fit
  • Full-length waterproof front zipper and taped seams
  • Minimalist bulk packs down to half-pocket size
  • Zippered access for jersey pockets underneath
  • Reflective elements to help maintain visibility
  • Castelli's latest effort to redefine inclement weather gear

Tech Specs

[membrane/laminate] Gore-Tex Shakedry (100% polytetrafluoroethylene)
Windproof Rating:
<1 cfm
Claimed Weight:
[size large] 123g
Recommended Use:
Manufacturer Warranty:
1 year

Size chart


Men's Apparel
Chest 36.2in
Waist 31.5in
Hip 37in
Inseam 31.9in
How to Measure:
For best results, take measurements over your underwear.
Measure under your arms, around the fullest part of your chest.
Measure around your natural waistline, keeping the tape a bit loose.
Measure around the fullest part of your body at the top of your legs.
Using pants that fit well, measure the crotch seam to the bottom of the leg.

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Superb !

  • Familiarity: I've used it several times
  • Fit: True to size

This jacket is very impressive. It is cut close and trim for road cycling, which eliminates any flapping. It packs down to the about the size of a standard PBJ sandwich, smaller than a typical SS jersey. It’s extremely lightweight. It functions quite well as a cool-weather wind jacket at road speeds with added wind speeds ranging up to 30 mph (net pushing 50 mph). And in steady light rains it has proven completely waterproof, no breakthrough anywhere, for rides lasting up to ~ 2 hours. The single zippered vent on the right-side back allows you to reach your rear jersey pockets, and extends the comfort range on the high side by allowing for some reasonable ventilation. What makes it even more impressive is it works so well without the typical sweatbox overheating I associate with Gore-Tex jackets. This thing actually breathes, while being as waterproof as any jacket I have ever owned. Finally!

The comfort range depends on air temp, winds, and sun exposure. As a wind jacket on clear, sunny days, it remains comfortable and dry inside with a fall/spring short sleeve base layer (Assos 2.4) and short-sleeve summer jersey (Assos Mangusta) in the range of ~ 50 to ~ 60 °F. In gray, overcast, foggy conditions with steady light rain, moderate winds (6 mph) I’ve found it comfortable and dry with the LS version base layer and same jersey up to ~ 68 °F. I’ve not yet pushed it beyond those ranges on either the high or low side.

The fit is trim, without any excess fabric to flap in the breeze. It’s cut for road cycling in a fairly aggressive position. The size chart worked perfectly for me. All-in all, a superb piece of gear.

Hi CC, I am 6ft 2" with a 40" chest and 35.5" waist. Not sure if I am a Large or XL in the idro, any guidance would be appreciated!

Hi Beth, based on both fit characteristic of Castelli and your dimensions, I would recommend an XL. Also, given that this an outerwear item that may be worn with more than just a summer weight jersey underneath and possibly worn with a base layer paired with a winter long sleeve jersey may make the Large size a bit restrictive.

Feel free to hit me up directly for more information and I would be happy to answer any questions for you.

John McKone- Competitive Cyclist Sales Solutions