The Spatz Basez Extreme doesn’t look like most base layers, and that’s because it isn’t. It’s thicker, heavier, and feels more like a piece of technical armour than a simple thermal top. Built for deep winter riding, it combines a windproof chest panel with a dense, waffle-knit fabric designed to trap warm air and wick away sweat, promising to “change the way you dress for winter riding forever.” That’s a bold claim, but after more than a year of testing across countless cold, wet miles, I can say this much – it really does make you rethink what you wear when the temperature drops.
Bottom Line
The Spatz Basez Extreme is the warmest, most substantial base layer I’ve ever worn. It’s designed for riders who refuse to stay indoors when the weather turns grim, and it succeeds brilliantly in that role. With its heavy-knit fabric, tall neck, and windproof chest panel, it delivers insulation you normally only get from layering two or three garments.
It’s not the softest or easiest to pull on, but once it’s on, it feels like winter armour – tight, protective, and ready for whatever the ride throws at you. If you’re a high-intensity winter rider, it’s one of the few base layers that can genuinely let you ditch a full jersey or jacket and still stay warm. At £139.99, it’s expensive, but its unique performance and versatility make it stand out.
Design and Fit
The Basez Extreme is built around a tubular, one-piece body made from polypropylene, elastane, and polyamide, with the arms, high neck, and windproof front panel stitched on. The fabric is densely woven with a waffle-like texture inside and out. On the inside, raised ridges form channels that trap warm air while moving sweat away from the skin. On the outside, the same pattern gives it a distinctive industrial look, broken up by stretch panels at the elbows, shoulders, and high-movement zones.
The fit is snug, even compared to other high-performance base layers. It’s a real pull-on affair the first few times – tight, compressive, and with sleeves that need adjusting into place. Once you’re in the riding position, though, it feels spot-on. At 176cm and 63kg, I tested a size small, and the fit was close without restricting breathing or movement. If you have a broad chest or prefer a looser feel, sizing up might make sense.
It’s easily the heaviest base layer I’ve come across – 246 grams in a size small, which is more than some long-sleeved jerseys. But that’s part of the point. It’s designed to replace an extra layer, not sit quietly beneath two or three others. The build quality is excellent, with no fraying or pilling after months of washing and wear. Some seams are a little thick, but none have caused irritation, and there are no tags, with washing instructions printed on the inside of the cuff.
Visually, it looks and feels premium. The subtle branding across the shoulder and back panel gives it a technical, understated aesthetic that suits Spatz’s no-nonsense design philosophy.
Performance on the Bike
This base layer shines when conditions are cold, dry, and demanding. Worn under a winter jacket or mid-layer, it delivers a deep, lasting warmth that never tips into overheating. The windproof chest panel does a great job of cutting out chill from headwinds and descents, while the thick weave keeps your core toasty.
More interestingly, it also works brilliantly when worn with less. On harder efforts or interval sessions, I’ve often used it with nothing more than a gilet or thin shell on top, and it’s been spot-on in temperatures around 5°C. The heavy-knit construction means it behaves like a base layer and jersey combined – warm, close-fitting, and surprisingly breathable.
It’s not a delicate piece of kit. It feels robust and slightly overbuilt compared to the silky comfort of something like an Assos Winter Skin Layer. But that ruggedness makes it versatile. It doesn’t cling to sweat or lose its warmth when damp, and it handles repeated wash cycles without complaint. It’s the kind of garment you pull on when you know the conditions will be foul and you want to forget about what you’re wearing once you roll out.
Comfort-wise, it’s not plush or luxurious, but it’s effective. It’s the difference between a base layer that feels nice and one that performs superbly. The snug fit keeps the fabric flush against your skin, maintaining warmth and ensuring moisture wicks efficiently. After a few wears, the material softens up, and any stiffness disappears.
Real-World Use and Versatility
The Basez Extreme’s biggest strength is how it lets you simplify your winter layering. With most base layers, you’d need a thermal jersey and a gilet or jacket on top for sub-10°C rides. Here, you can strip that back – a gilet and this base layer are enough for tempo rides or efforts in near-freezing conditions.
On long winter miles, it pairs equally well under a proper jacket. The warmth-to-weight ratio is unmatched, and it keeps its insulating ability even when you start to sweat. That combination of breathability and protection means you can push harder without feeling clammy or chilled.
The tall neck is another thoughtful detail. It seals out drafts and adds noticeable comfort on long descents or windy days, reducing the need for a separate neck warmer. The dropped rear hem also integrates neatly with bib tights and jackets, preventing gaps or drafts at the lower back.
No, it isn’t waterproof, but paired with a water-resistant outer layer, it handles drizzle and spray comfortably. For racers and fast group riders who generate a lot of heat, it’s a rare piece that lets you go light without getting cold – and that’s where its real appeal lies.
Value
At £139.99, the Basez Extreme sits at the premium end of the base layer market, but its value lies in what it replaces. It’s not just another thermal layer – it’s warm enough to let you skip a jersey or heavy mid-layer entirely, which can simplify your winter wardrobe. Spatz often discounts its products, and even at full price, the performance justifies the cost for serious winter riders.
If you’re simply looking for an affordable warm layer to wear under a jacket, there are cheaper options from Castelli, dhb, and Endura that will do the job. But if you want a piece that genuinely changes how you dress and perform in the cold, the Basez Extreme is worth the investment.
Pros and Cons
Pros
- Exceptionally warm, heavy-duty construction
- Windproof chest panel for added protection
- Can replace a full jersey or mid-layer
- Excellent moisture management and breathability
- Durable and well-made, washes well
- High neck and dropped rear provide great coverage
Cons
- Expensive compared to standard base layers
- Very tight fit may not suit everyone
- Heavy and less soft than lighter options
- Slightly bulky seams inside
Conclusion
The Spatz Basez Extreme isn’t just another winter base layer – it’s more like an entire winter system in one garment. It’s warm, protective, and built to handle the coldest, toughest conditions without relying on multiple layers. It won’t win points for softness or lightness, but that’s not what it’s about. It’s about confidence, comfort, and control when the temperature drops close to freezing.
For riders who spend the winter months training outside, tackling long rides, or racing through cold air, it’s one of the most capable and distinctive pieces of kit available. Once you’ve worn it, you’ll rethink how much clothing you really need for winter riding – and you might never look at your other base layers the same way again.
