Koo Demos Sunglasses with Red Mirror Lenses

There's something about cycling glasses – the function that necessitates their form means they don't look great in isolation. Walking down the street on a summer's day in the Koo Demos would, I feel, attract some confused looks, they're so big and so shiny. When paired with a helmet, though, it really completes the aesthetic and balances out their bulk, and I think they look the business. And they have the performance to match.

If these are beyond your budget, or just not to your taste, check out our guide to the best cycling sunglasses for more options.

> Buy now: Koo Demos Sunglasses with Red Mirror Lenses for £170 from Chain Reaction

I grew up as the Oakley brand was exploding, forever changing the sunglasses industry in two ways: they made 'sporty' shades cool, and they popularised the semi-indestructible properties of polycarbonate lenses – who can forget the marketing campaign where Oakley lenses withstood a shotgun blast?

The Koo Demos sport a polycarbonate lens, rather than the inferior CR39 plastic found in purely 'fashion' glasses, which is deeply reassuring. They've so far shrugged off the grit and any wayward small stone that's hit them, though they haven't been tested by anything larger or moving perilously fast. But I certainly wouldn't trust my eyes to anything that wasn't polycarbonate.

For optics, Koo has partnered with Zeiss, a German company founded nearly 180 years ago, whose name is more or less a byword for fineness and precision in lenses. I found the glasses to be optically flawless, and as far as I could tell, 100% distortion free, even with their generous curve.

The stylish red-mirrored versions on test are rated as 23% VLT (visible light transmission), meaning they're considered a 'medium' in terms of light transmission, and well suited to medium to high amounts of sun; essentially, any time there's direct sunlight, either breaking through clouds, or full beaming sun, these are going to be perfect. In the limited spring sunshine we've so far had, I've really enjoyed them; optically they're excellent, nice and sharp, and they seem to be contrast enhancing – they make the edges of things look more defined, which is a great help in bright light, and when moving in and out of sunshine.

There's quite a lot to like about these Demos, and one or two things to note before purchase.

In the pros column, the four vents on the front prevented any fogging at all, and I found the airflow also contributed to keeping sweat out of my eyes. Nice.

The glasses are around the same weight as other expensive sunnies we've tested; they're lens heavy, which is unsurprising and actually confidence inspiring – I certainly wouldn't trust my peepers behind flimsy weightless plastic.

Your mileage may vary in terms of fit, but for me they were great. I thought them a bit high when I first put them on, but the moment I got into the saddle and bent forward, I found I was looking through the top part of the lens anyway and very grateful for the extra size above my eyeline.

The nosepieces are lovely, and click to give two 'settings' of adjustment. I found them and the grippers on the arms both soft and grippy enough to prevent any slippage, even when climbing out of the saddle.

The Demos come in 12 colour frame/lens pairings ranging from £140 to £170, and other lenses can be bought separately from £35-£45 in 11%, 23% or 58% VLT. There's also a photochromatic version for £79.

As I say, I thought they were great. Really sharp, really clear, really comfortable, and so far unscathed by road detritus flung their way.

However, there are two small issues, both of which are trade-offs, compromises intrinsic to such a big piece of polycarbonate, and that's reflected light. I found there was a noticeable amount of reflected light on the inside lower section of the lens. This is almost unavoidable with designs such as these, and the Demos are coated on the inside to minimise this. They're among the best 'sports' glasses I've tested at mitigating this, but it'll certainly come down to how closely they fit you.

Secondly, the reflective coating on the outside of the lens (unsurprisingly) reflects light. I found this was visible when riding into the sun particularly, as a line of light visible through the glasses, which moves as you move your head. For me, that line sat about two-thirds of the way down my vision and was both noticeable and slightly distracting. It comes and goes, and I mostly was able to ignore it, but it should be noted if you're buying your first pair of big lens glasses.

There's a video below that shows this perhaps better than I can describe. Again, an inevitable by-product of that stylish coating.

Finally, and this may be a room-splitter: there's no polarised lens option. Some will tell you that polarisation is unwanted in cycling glasses; by nature it cuts out glare and reflected light, particularly off water and snow, which means they actually hide errant puddles on the road, letting you see right through them and making them harder to spot, which some find undesirable. For riding in cities, though, I've noticed how brilliant polarisation is, cutting light reflected off car windscreens, and the tonnage of glass from buildings around. If Koo did a polarised version, I'd certainly pick up a lens for city riding on sunny days, and all the coastal riding I fantasise about doing too...

Value and conclusion

You don't need to spend £170 to get a good pair of sunnies – you can get a lot of value and function from the Pandas that Lara loved, for example, and they're half the price.

But while these sit in the upper range of the market, competing with the likes of Oakley, Roka and Sungod, they come in cheaper than quite a few. Stu loved the Oakley Katos, for example, but they're £245; the Roka GP-1Xs that Mat tested a few years ago are £225, and the SunGod Airas that Anna tested start at £180...

All in all, these glasses are very good. If Koo ever makes a polarised lens, I'd buy it, and think that'd be about as good as glasses got!

Verdict

Great glasses, specialised optics and pleasing in use – quite stylish for cycling sunnies, too