Founded in 2016, Koo is a relatively new cycling sunglasses brand from the maker of Kask helmets. Its flagship model, the Koo Open, was well received and now the brand has launched a half-frame iteration of this model called the Koo Open Cube (or ‘Open3’, as is printed on the sunglasses).
Made in Italy, the Open Cube features a large one-piece lens clipped into a solid, but very lightweight frame. These shades weigh next to nothing—a pair of size mediums, for example, will tip the scales at just 35 g.
As the first half-frame sunglasses I’ve tested, the spacious feeling that I felt when I initially tried them on took me by surprise. The frame and lens comfortably wrap around your head and fit like a glove, with the outside edges of the lens well outside your field of vision. Whenever I switch back to my trusty Oakley Split Jacket now, it takes me a while to get used to the frame blocking the edge of my vision.
That leads us nicely on to the star of the show: the lens. Manufactured by legendary brand ZEISS, known for high-quality camera lenses, it’s an impressive bit of kit.
It’s the clarity of the lens that really stands out. There is not even the slightest hint of distortion across the whole visual field. In fact, when I first tried the infrared lens, that came with the white frame I tested, the image was so clear and the colours were so true that I wasn’t convinced the 19% visible light transmission rating was accurate.
Thankfully, my concerns were quickly quashed; the lens provides great protection in sunny conditions, and I’ve even read of people using them while skiing with no issues. I tested the Open Cubes in a variety of variable light conditions, and the lens performed flawlessness—eliminating glare and maintaining clarity throughout.
The reason I was initially so surprised by the clarity of the lens was that, compared to other sunglasses brands that I’ve tested (like Oakley and Electric), the ZEISS lens doesn’t mess around with (or ‘enhance’) the contrast. Instead, it seems to block all colours of light equally, maintaining a balanced and neutral tone. Whether this is something you like is down to personal preference, but it feels really natural to me.
As with many other high-end cycling sunglasses, the lens in the Koo Open Cube is interchangeable. This was a slightly nervy process the first time because I didn’t want to damage the lens, but it turned out to be really easy. Simply hold the outside edge of the lens and pull it away from the frame. Then, reverse the process to snap a new one in place.
The Open Cube is available in a range of colours, each with a corresponding standard and low light lens. Replacement lenses are also available, currently priced at around £50 for a standard lens and £40 for a low-light lens. A photochromatic lens, that adapts to changeable conditions, is also available for £55.
Yeah, that’s expensive, however, due to the clarity of the standard lens, I found that it worked better in lower light conditions than other brands I’ve tested. So, you may not have to swap lenses as much as you’re used to.
Aside from moving to the half-frame design with the Open Cube, Koo has also added ventilation notches at the sides and across the top of the lens.
Despite this, the close-fitting, wrap-around design does an amazing job at protecting your eyes from the wind, dust and those pesky bugs.
Overall, ventilation seems to work well. Occasionally I did find that there was a tiny bit of fogging around the edges of the lens, when I stopped cycling, but this was swiftly cleared up as soon as I started moving again and the airflow resumed.
Airflow is also aided by the ingenious pivoting arms. Instead of folding, like traditional sunglasses, the arms on the Open Cube ‘rotate’.
This allows for the lens to be tilted at three different angles to provide additional ventilation and a better fit for your face shape. It’s a small detail, but one that I found useful. The perfect fit is further helped by the specs coming in two sizes and an Asian specific shape.
The arms are flexible and have inset rubber grippers that comfortably secure the sunglasses around your head. These are an expensive pair of sunnies, so the last thing you want is for them to fall off.
It’s a bit unconventional, but to test this I wore the Koo Open Cubes while doing backflips on a trampoline. Normally, the centrifugal force would rip my go-to pair of sunglasses from my face, but the Open Cubes stayed firmly wrapped on my head—that’s a big thumbs up from me!
Adjustable folding nose piece
The other point of contact on a pair of sunglasses is the noise piece, and Koo hasn’t skimped on design here either.
The shades come pre-fitted with adjustable nose pads that click back and forth between two positions. This means you can set them for a wide or narrow nose to further refine the fit.
You can also swap out the nose pads for a nose bridge. This also adjusts in the same way but holds the lens slightly further away for your face to allow more airflow.
Being made from a soft rubber material, I found that both the nose pads and nose bridge gripped my nose very comfortably without any undue pressure. After a while, it almost felt like I wasn’t even wearing sunglasses.
With a price tag of £180, the Koo Open Cube is unashamedly pitched at the premium end of the market. This will obviously be an important factor when choosing a new pair of cycling shades. However, when you compare the Koo’s crystal clear optics to those from a cheaper brand, there is no comparison; I’ve really started to notice imperfections in cheaper mid-range sunglasses.
So, if you’re thinking of picking up a pair of these shades, then it’s likely that you’ve also considered sunnies from other high-end brands such as Oakley and POC. Compared to these, I would say that the main thing to consider is whether you prefer your sunglasses to enhance colours (like Oakley lenses tend to do) or maintain a neutral tone (like the ZEISS lens in the Koo Open Cube).
Again, this is a personal preference, but as a longtime Oakley user and having tested the Open Cubes, I’m making the switch.
If you’re looking for the perfect bike helmet to pair with the Koo Open Cube sunglasses, check out my review of the Kask Mojito road cycling helmet.