At road.cc every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.
Good scores are more common than bad, because fortunately good products are more common than bad.
The Assos Women's Ultraz Winter LS Skin Layer is top notch in every aspect – fit, comfort, warmth and moisture management, and durability looks to be good too. Its price tag is also on the top notch. But this isn't an everyday baselayer, it's designed for 'your coldest rides' and 'the most challenging winter conditions'. If your riding doesn't stop whatever the weather, the Ultraz is well worth considering.
The Skin Layer is successor to last season's Skinfoil. Assos claims that it's 'about 10% lighter' than the Skinfoil (the non-Ultraz version is 'roughly 13% lighter'). The seamless construction remains the same, but the composition is significantly different, with wool (31%), polyamide and carbon fibre added into the mix – a 'robust arctic-tuned blend' according to Assos.
The weather has been great for testing over the last few weeks: the Ultraz is at its best in temperatures from 6°C down to freezing on the road – and lower than that if you venture onto trails. It's only when the mercury has approached double figures that I've found it too warm (worn under a jacket I would normally team with a standard polyester baselayer and be 'just right'). That would seem to confirm its 3/3 rating in Assos' Layering System.
The high neck is very snug and really does give the baselayer a winter feel. I found I didn't need to add a neck warmer, as I normally would when riding in figures close to zero. But it does emphasise the Ultraz's 'only cold weather' tag: I found it a little stifling in anything above 8°C.
I haven't suffered with moisture build-up at all, even when working hard – it handles sweat well. Unlike some tops, there's no rapid cooling off or sensing of a damp chill if you stop for any reason mid-ride. Maybe this is the carbon fibre content working. I'd say Castelli's Prosecco Tech layer is as good at handling moisture, but it's nowhere near as warm.
The fabric itself is very giving and soft, hugging the figure without any pinching or irritating. It doesn't offer compression – it's skin tight without being restrictive.
If you use the size guide on the Assos site, it takes into account your height, weight and age. I came up as needing a medium (sizes, S-L, are labelled 0, I and II by Assos) and for me the fit was perfect. I'd say it's worth using Assos' guide too, as the length is important here because it doesn't have a drop at the rear and you don't want to be left short (some online outlets might only use chest measurements).
On me there was just enough length in the body and sleeves. I tested it with both bib and waist tights. The stretch in the fabric means you can easily pull it down to tuck into the waist band of your tights, and I never had an issue with it riding up, though this could depend on your tights.
I don't tend to suffer with irritation from side seams, so the boast of there not being any didn't cause huge excitement, but I have to say it is noticeably more comfortable than having seams.
The 'circular seamless construction' makes little difference here aesthetically, given you'd be wearing it with a winter jersey or jacket, but I can see it could be useful in the short-sleeved versions also made this way, under a skin-tight short-sleeve jersey. Naturally, there are seams at the base hem, cuffs, neck and shoulders, and they are all very tidy.
One thing worth noting with regards to the seams is that they have plenty of give – some baselayers have seam stitching that doesn't stretch and can pull on panels of fabric, creating weakness at the seam and, worst case scenario, actually snap the threads. There's none of this with the Ultraz.
Instructions are for a 30 degree wash, no softener, so just like most cycling kit. The wool content of the layer is a big plus here – I've been getting several wears out of it before throwing it in the laundry. This is certainly a win over fully synthetic layers that can be smelly after one wear.
There's no denying that the Ultraz Skin Layer is an expensive bit of kit, and you can certainly pay less, even for some high-end options. The GripGrab Freedom Thermal base is one of the closest, boasting a similar seamless construction, for £90, while Rapha's Women's Pro Team Thermal Base is £70.
But Assos sees this as 'the ultimate defensive first layer in the most challenging winter conditions'. If you don't need that, its non-Ultraz version is £85. (And you can spend more – Rapha's Men's Deep Winter Windblock Base Layer is £130, though it does, as the name suggests, have a windproof panel at the front.)
There are plenty of cheaper options for winter training, though. Craft has some great layers – Ashley got on well with the men's version of the Active Intensity CN LS Layer, and there's a similar women's version for £40. dhb's Merino Layer is also an option for £45, and you can go cheaper still with Decathlon's Van Rysel women's base layer for £29.99, which even comes with a two-year warranty.
While I've been bowled over by the performance and quality of the Assos Ultraz, personally I'd struggle to justify the expense, especially given the range of alternatives at much more palatable prices. However, there's no denying it's a very good piece of kit when the weather is raw, and if you like to rack up the miles in some seriously low temperatures, you might consider the investment money well spent.
Faultless performance and comfort – but you have to dig deep to pay for it
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road.cc test report
Make and model: Assos Women's Ultraz Winter LS Skin Layer
Size tested: I
Tell us what the product is for
Assos says, 'Our Women's Ultraz Winter LS Skin Layer brings maximum thermal protection and body-mapped comfort to your coldest rides, courtesy of our new wool-blend knit and seamless design.
'With its wool-blended knit, the Women's Ultraz Winter LS Skin Layer turns up the warmth and windblocking capabilities to the max. We see this as the ultimate defensive first layer in the most challenging winter conditions, as it goes into overdrive at the core level to keep you dry and your temperature stable.
'Setting a new foundation, this Skin Layer is a total reset on our base layers of yore, wearing a completely revamped, female-specific makeup and using a new blend of fibers. The Ultraz model is about 10% lighter than the previous Winter LS Skinfoil, relying on a Circular Seamless construction that's both ultrasoft and free of irritating side seams. A robust arctic-tuned blend of polypropylene and wool are also employed, serving as the ultimate next-to-skin foundation when maximum thermal- and windblocking- protection are most critical.'
Tell us some more about the technical aspects of the product?
Circular Seamless: A tubular knit technology that's free of side seams, creating an ultrasoft, comfortable feel against the body.
Raglan Cut: Sleeve design free of a traditional shoulder seam, continuing up to the neck for greater range of motion.
Composition: 50% polypropylene, 31% wool, 10% polyamide, 6% elastane, 3% carbon fiber
Minimal seams are neat and clean.
Does a great job of keeping you warm and handling moisture.
Has been worn virtually every day during the test period, granted only a month or so, but showing zero signs of wear.
Stay true to size and try to use Assos' guide over outlets that might rely solely on a chest measurement.
How easy is the product to care for? How did it respond to being washed?
Very easy. All printed on the fabric to avoid an irritating label. Its wool content means odours don't cling to it as they might a fully synthetic one. I was getting several wears out of it before it got thrown in the laundry.
Tell us how the product performed overall when used for its designed purpose
Comfy and very warm with great moisture management.
Tell us what you particularly liked about the product
Snug fit without pinching or irritation. Warmth.
Tell us what you particularly disliked about the product
Nothing, bar the price.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
In short, it's expensive. You can get close to its price tag with something like GripGrab's Freedom Thermal base for £90, or Rapha's Thermal Base for £70, but then there's Assos' non-Ultraz option at £85. Rapha's Men's Deep Winter Windblock is £130.
Did you enjoy using the product? Yes
Would you consider buying the product? No
Would you recommend the product to a friend? If they were willing to spend that much, yes.
Use this box to explain your overall score
Its performance really is faultless and the fit was spot on for me, but it comes at a fair old price. Bearing in mind that it's really only suitable for riding in very cold weather, it's not the most versatile choice, but if you're serious about your winter riding and can afford it, it's very good.
About the tester
I usually ride: Road My best bike is: Carbon road.
I've been riding for: Over 20 years I ride: Most days I would class myself as: Expert
I regularly do the following types of riding: commuting, touring, club rides, general fitness riding, Getting to grips with off roading too!
Emma’s first encounters with a road bike were in between swimming and running. Soon after competing for GB in the World Age Group Triathlon Championships in Edmonton in 2001 she saw the light and decided to focus on cycling.
After a couple of half decent UK road seasons racing for Leisure Lakes, she went out to Belgium to sample the racing there and spent two years with Lotto-Belisol Ladies team, racing alongside the likes of Sara Carrigan, Grace Verbeke, Rochelle Gilmore and Lizzie Deignan. Emma moved from Lotto-Belisol to Dutch team Redsun, then a new Belgian team of primarily developing riders, where there was less pressure, an opportunity to share her experience and help build a whole new team; a nice way to spend her final years of professional racing.
Since retiring Emma has returned to teaching. When not coercing kids to do maths, she is invariably out on two wheels. In addition to the daily commute, Emma still enjoys getting out on her road bike and having her legs ripped off on the local club rides and chain gangs. She has also developed an addiction to touring, with destinations including Iceland, Georgia and Albania, to mention just a few. There have also been rare sightings of Emma off-road on a mountain bike…