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LATEST UPDATE FEBRUARY 5th 2026
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Castelli Alpha 150 Jacket
380g XL Deep Burgundy/Clay (as tested) £360
The Castelli Alpha 150 Jacket is a beautifully made and very well-thought out winter jacket for those who want a racing fit (or have the figure to pull it off) for speedy jaunts when the weather turns cold. With dual-layers, dual zips, water resistance, well-specced fabrics, and more traditional features, it comes at a price – although it is discounted at the time of writing. Some may baulk at that, others may have found their dream partner – at least for the colder months.
Pros: high manufacturing values, dual-zipped and dual-layered for enhanced climate control, double-ended outer zip, snug fit, great waist gripper strip, water resistant.
Cons: be careful with sizing, price.
Specification
Aimed at the sportier rider – the snug fit and stretchy fabric say it all – the Alpha 150 Jacket is described by Castelli as their “best winter jacket ever.” They say it has been twelve years in the making, the product of experience and innovation. So, what do you get?
The most obvious feature is that there are two layers, not separable, but designed for temperatures from -2C - 10C. the jacket is water-resistant; Castelli claim that all but the heaviest showers will be kept out. You could take this to mean either check the weather forecast or don’t forget your rain jacket.
The outer jacket is made from 150g Polartec AirCore, exclusive to Castelli offering protection against the elements but also breathable. The inner, stitched in at the back but open at the front is Polartec Alpha, which is warm but allows moisture to escape. There’s plenty of green cred, if that’s your bag, as the jacket is made from recycled yarns and is free of PFAS.
The outer and inner have their own zips. Several options present themselves regarding temperature control. Work them out and enjoy the flexibility. The outer zip can be opened from top or bottom. The layers should, of course, help trap air to add to the warmth given by the fabric. On the topic of trapping, there’s a sturdy gripper strip. This is rubber at the rear to keep that drop-back solidly in place.
The traditional three rear pockets are supplemented by a valuables pocket with a zip. Finished off with three rear pockets for essentials, a zippered valuables pocket. There’s not much in the way of reflectives, but the piping along the bottom of the pockets is helpful. Cuffs are described as “glove compatible.”
Sleeves are not overly long, nor collar especially high; this is a pretty understated garment. Stitching and other aspects are of a very high standard, with no prominent seams pestering the rider, even when the stretchy fabric envelopes snugly.
Size and fit 3.75/5
This is a racy garment with a suitably slim fit. Don’t be vain, be realistic. I am no lithe racing snake. I generally take a large fit when it comes to touring gear, but this is a definite extra-large for me. It still feels snug, so I’ll not be denied another personal best by resistance – it’ll be too hearty a Christmas and lack of training that does that. The zips are good and strong, the fabric is stretchy, but I’d say I am pushing the envelope, as they say. I am inclined to think that an XL would not have been out of place. Mind you, I’d be willing to diet for £360!
The big point is that you should follow the Castelli sizing guide and be ready to go up a size if necessary. They ask prospective purchasers not to go on what is their norm, but to check measurements out carefully. Certainly, the sizing guide is very detailed.
Care and durability 3.5/5
As with most technical garments, a cool wash is required, but there’s no inherent reason why it can’t go in the general laundry. However, whist I’m sure the instructions are spot on, I’d tend toward mild detergents, not least because I’d feel incredibly stupid if I managed to wreck my investment. I have washed the jacket inside out with zips done up.
Again, following the usual pattern, avoid conditioners, bleach, tumble-drying etc. Ideally it should be dried line dried in the shade. Given it has been a cold and very wet testing period, I’ve not had much chance to try this out – not outdoors anyway. Indoors, with the central heating on, it has only taken some three hours to four hours for it to dry (it had been through a spin cycle). This came as a pleasant surprise, given the dual-layer design. Without the central heating, I suspect it would have dried overnight.
I’ve worn it almost every day – on and off, and not in bed – and it still looks as good as new. I’d expect that to be honest, but after a few washes one may find some bobbling or the odd loose thread. Not here.
Performance 4.75/5
Comfort is what one expects, along with a high level of function. I’ve not been disappointed by either, but it is well-worth remembering that even a jacket like this needs to be part of a system that works together to keep the cold and damp out when the weather turns really nasty.
First trip out, the Alpha Jacket next to the skin with a waterproof jacket over the top, was in storm Chandra with heavy rain being driven by 44 mile an hour winds and a wind-chill supposedly taking things down to -9C. I doubt the latter, but not a bad baptism. Things felt a bit chilly, bit that was soon overcome. The ProViz 360 waterproof jacket is not the most breathable and the vents had to be closed, but at no point did I feel clammy, although on arrival the inner mesh of the ProViz was damp with sweat. Learning point; best with a more technical waterproof jacket if needed.
Next up was a dry ride with the temperature hovering around 0C. this time, the Alpha was on top with the Castelli Flanders 2 base-layer underneath. No rain, but a distinctly chilly morning. Once underway, things quickly warmed up with initial chill being dispelled. A couple of hours later, comfortably warm, with the temperature rising to 2C, I felt very comfortable churning away uphill. Of course, there’s a bit of a chill on those descents, but nothing to take exception to.
When things become sweaty, wicking kicks in to dismiss clamminess with alacrity. Seventy-five miles around rolling Cheshire, Shropshire, and a little bit of Wales, with a couple of hours of heavy rain making the 3C high feel even less comfortable, felt pretty sweet (Flanders 2 base-layer and Showers Pass Elite 2.1 jacket sandwiching the Alpha 150. Yes, moisture built up on the ups and there was a chill when stopping before getting into the café, but I never felt clamminess.
At 1C, overcast, but dry, I went without the jacket. With base-layer and Alpha alone, I can’t say it was a toasty start, but once into a decent cadence, things soon became comfortable. I’ll admit to a preference for feeling a little cooler than many, but who wants to become too sweaty when churning away on a winter’s day. I’d still keep a jacket to op[o on in case there are any pesky stops for roadside maintenance.
On the odd warmer day, I’ve been tempted out without a base-layer, hoping the temperature would muster 8-9C. this has only happened once during the testing period. Overall, fine, although roadside stops could get chilly. I’d be inclined to keep the vase-layer and paly with the various zip positions of inner and outer to temper the climate.
I have several jackets which are longer in the body, but I’ve not found that too much of a problem with the Alpha 150. The waist gripper is excellent and, in any case, the Alpha 150 lends itself to bib-tights.
The collar forms a good seal, too, and paired with a base-layer with a decent collar (I’ve found Sportful’s Sottozero Base Layer great and the aforementioned Flanders 2 ideal), keeps the cold at bay with seemingly little effort. As for those “glove compatible” sleeves, they slip very nicely under the cuffs of winter gloves, notably the Castelli Estremo. These come with a gusseted cuff and a hook ‘n’ loop closure, strengthening the barrier against the elements. Tucking the sleeves into less generous gloves is marginally trickier, but not a problem. The Alpha’s cuff is helpful here, with an inner that extends beyond the outer.
The Alpha 150 is described as water-resistant. That’s fair enough. For speedsters ‘resistant’ can trump ‘proof’ because of better temperature control. So great for faster rides when you won’t be out in the rain all-day. Drizzle, periods of light rain, a short sharp shower, and you’ll probably be ok, with things drying pretty rapidly when the rain stops. However, if longer spells of rain are likely or if it is a hefty downpour you may want to seek shelter or have the rain jacket with you.
Pockets will take the regular stuff needed for a winter jaunt. The snug fit aids security of tenure. The secure zip-pocket is on the hip, which I rather like. Easy to access the credit card at the café if I don’t manage to find a way of getting others to pay.
Despite the dual-layers, the Alpha has never felt cumbersome when adjusting positions on the bike. On the contrary, it feels almost like a second skin.
Value 3.75/5
£360 is undeniably a hefty whack to shell out for a cycling jacket – even a sophisticated one. However, if you want a very well-made, winter jacket, with flexible options for climate control, and you are training or racing or just want to go fast, then this could be your dream. You may well find it discounted, too.
The Sportful Total Comfort Jacket come in a tad under £300 (can be discounted if you look carefully) and performs very well in winter conditions, although I’d give the Alpha 150 the edge when it comes to protection form the elements.
The MAAP Winter Training Jacket (£270, now reduced to £130 doesn't have the same temperature range - on paper better suited to slightly warmer ends of the early season (6-15 degrees) A slightly different take on the winter jacket is Galibier’s Libetre Packable Jacket - seemingly very practical and comparatively inexpensive at £82. Altura have something similar in their All Roads Men's Packable Insulated Jacket.
If you’re looking for a waterproof shell, then Gorewear’s Swiftride Jacket comes in at £209.99.
Summary
Whilst I can see some uses for winter touring, the Alpha 150 is better suited to a fast club runs and speedier day rides, as opposed to loner trips with more faith in the weather forecast. You can always stick that ultra-light rain jacket in a pocket. You’ll still need layers, but fewer, and you’ll have lots of options if things warm up.
