Castelli Alpha RoS 2 Jacket Men’s

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 calls the Alpha RoS 2: "[Our] ultimate jacket, bringing warmth, breathability and a high level of rain protection along with a soft, comfortable fit. With a fresh update in its third generation, this jacket leads the way in demonstrating how a winter jacket should perform."

If you'd like more detail, Castelli offers a huge writeup.

"This jacket is exactly what we think the perfect winter jacket should be. We started with a list of things we didn't like about the current jackets and set out to solve them''and in the process make our best jacket ever.

"The first issue to resolve related to moisture management. Even the best of the currently available fabrics provide a good level of breathability but can't keep up with the sweat generated during high-intensity riding. So we invented a double-layer construction that allows you to open an outer wind-protection layer while keeping the insulation layer closed and thereby allowing airflow inside the jacket to evacuate moisture while avoiding direct contact with the skin.

"On a long climb we'll completely open the outer layer to allow moisture to escape, and when we start the descent we close the outer layer and are completely dry inside. It works so well that sometimes it feels like magic. New for this year is a softer, warmer 3D insulation-layer fabric that provides better warmth, moisture management and fit.

"Next we focused on the openings: neck, waist and, most of all, wrists. The neck comes up high and is shaped to move with you, whether you're standing or in an aero position being a January hero and attacking your mates.

"For the waist we've created a stretch layer with a silicone bead that lies flat and completely seals out wind without bunching or riding up.

"New for this year is a brand-new double-layer wrist opening with an inner layer to go under your glove that seals tight to your wrist, and an outer layer that goes over your glove so that any rain will roll down the outside of the glove and not end up inside.

"Of course, the ultimate jacket will also hold up well in wet conditions, so we used Gore-Tex Infinium WIndstopper fabric along with waterproof seam taping on critical seams around the shoulder. Other seams are hidden out of direct water flow, and the water-repellent treatment on the fabric is sufficient to prevent most moisture from entering. We call it essentially waterproof, using our own subjective judgment to find a balance between water protection, breathability and comfort. It doesn't mean that no drop will ever come in, but we do longish rides in real rain and stay completely dry.

"All these features make it a favourite of the Team Ineos riders, and the most versatile performance jacket for cold-weather training we've ever created."

Castelli lists these features:

Rain or Shine engineering makes this our best jacket ever for dry conditions while also providing significant rain protection

Gore-Tex Infinium Windstopper 150 fabric for wind protection with high breathability and effective rain protection

Reduced seaming with seam sealing on shoulders reduces chances for water to enter through stitching

Double-layer Alpha construction separates insulating layer from wind/water barrier to let you better regulate ventilation

Water-resistant YKK Vislon zipper slides easily for better regulation of airflow

Raw-edge waist with silicone gripper lies flat and seals out wind

Double-layer cuff integrates with glove to prevent cold wind or water from entering at wrist

Stretch fabrics with advanced patterning make for excellent close-to-body fit that still accommodates a wide range of body types

Back ventilation

3 rear pockets with reflective laser-cut drain holes

Zippered secure side pocket for valuables

-5°-10 °C / 23°-50°F

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

Gore-Tex says that its Infinium Windstopper garments are totally windproof, water-resistant, and very breathable, and the performance bears that out.

Gore-Tex says, "Created using an ultra-thin protective layer laminated to a lightweight textile, Gore-Tex Infinium Windstopper products are totally windproof. Although textiles such as microfibers, closely woven fabrics and many fleece materials are often termed windproof, even light winds can penetrate most of these fabrics, making you feel chilled and uncomfortable.

"By Gore's standards, a fabric can only be considered truly windproof if its air permeability is 1.0 cfm (< 5 l/m2/s) or less. It's a standard that our products easily meet.

"The membrane technology in Gore-Tex Infinium Windstopper products has billions of pores that are 900 times larger than water vapour molecules, so even though wind can't get in, moisture from sweat vapour can easily get out.

"In addition to the GORE membrane technology, a durable water repellent (DWR) treatment is applied to most of these products. This penetrates a jacket's outer fibres, lowering the surface tension so that water beads up and rolls off. That means less water accumulation, resulting in less wind chill, and less extra weight."

It's a clever construction, especially at the front where the double-layer design gives you different options to suit the conditions, terrain, and your riding tempo.

The new double-layer cuff design is smart too, stopping water from the sleeves going into the top of your gloves.

It puts in an exceptional performance across a range of winter conditions.

The fabrics have proved to be pretty hardwearing so far. I have a previous version of this jacket from a couple of years ago and that one is still looking good too, including the zip which is good news because it's a big problem if that goes.

Windstopper fabrics aren't intended to be fully waterproof. Rain can get inside this jacket eventually – you still need to carry a waterproof jacket if full-on rain is forecast – but water from spray and short showers beads up and rolls away.

The Windstopper fabric isn't as breathable as a non-membrane fabric, obviously, but it is impressively breathable for a windproof fabric.

I found the fit to be excellent – slim with enough stretch to prevent any rucks or ripples.

As described on Castelli's size chart.

The double-layer construction adds a little weight, but I'm not looking to save grams in a winter jacket, I just want it to keep me comfortable in various conditions.

I've found it comfortable in a variety of different conditions.

This is one of the higher-priced winter jackets we've reviewed, but the fabric tech, the construction, and the performance are all exceptional.

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

You wash it in the machine at 30° and it comes out fine.

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

Exceptionally well across a range of winter temperatures; it copes with showers well too.

Tell us what you particularly liked about the jacket

The versatility of the double-layer front, and the performance of the Windstopper fabric.

Tell us what you particularly disliked about the jacket

It's definitely worth the money, but paying this amount on a cycling jacket still hurts.

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

The Assos Mille GT Winter Jacket Evo we reviewed recently was £225, and Rapha's Classic Winter Gore-Tex Jacket is £270.

Use this box to explain your overall score

The performance is exceptionally good, and that's definitely worth paying for if you ride year-round whatever the conditions.