“Game changer” is not a term that should be used lightly. But it’s the best way to describe Castelli’s Idro 3 Jacket. It’s the most waterproof, most breathable, most compact jacket the company makes.

Ask most Castelli staff members what’s the one piece they couldn’t live without. Or what’s the first piece they recommend to their friends. Or what product has made the biggest difference in the way they ride. The answer will likely be the Idro 3.

IDRO 3 JACKET
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 center 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.

WHAT IT IS
This fully waterproof, highly breathable, and extremely lightweight and packable (half a pocket) jacket featuring an innovative fit system is perfect for any rain ride or long descent.

GORE-TEX® SHAKEDRY™
It’s a revolutionary fabric that Gore created by putting the membrane on the outside instead of sandwiching it between two textile layers. With the outer textile eliminated, the rain hits directly on the PTFE membrane, beads up, and literally just rolls off. Or you can shake it off! Having just two layers makes this fabric the most breathable waterproof fabric you’ve ever used. It’s not the clammy waterproof shell you’ve suffered with in the past.

PRODUCT FEATURES
> 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