Koo Open Cube sunglasses review

I have a small face. I'm average height, with average size feet and average sized hands - but finding glasses and helmets to fit me has always been a struggle. My standard approach is to order junior/youth or Asian fit options, but this does limit choice.

Enter: Koo, the glasses range from helmet giant Kask. These glasses have a lot going for them - they'd be a great buy for an individual with a 'normal' sized face too, but I'll start with their adjustability as it was the feature which impressed me the most.

Sizeable range

Koo makes its Open Cube glasses in a standard fit, split into Small and Medium, as well as an Asian fit, also split into Small and Medium.

I opted for the standard model in a size Small, and they fitted well, without any 'overlap' or concern over them slipping off my face. A comparison to the Oakley Radar EV Youth model showed these are very slightly wider.

The arms have flexible temples and they fold inwards, as opposed to outwards. The design allows for three distinct positioning options to help riders pair the glasses with a range of helmets. Regardless of arm placement, the frame did come quite high up my forehead, so the glasses slightly contacted my Specialized Evade helmet, but this isn't uncommon and would be less notable on a standard (non-aero) helmet.

The glasses come with an adjustable nose piece in two parts, and they're also shipped with a second option which sits in a single bridge. The latter lifted the glasses slightly further away from my face. However, in swapping the two-part version back on, I managed to break the rubber replacement bridge with relative ease, but we'll come to build quality later.

The Open Cube's are available in 12 different colourways and I chose blue/orange to match my team kit.

Zeiss tech lenses

Koo has reached out to specialists Zeiss to create its Open Cube lens. These glasses come with an 'Ultra White'  shield as well as a clear option for winter rides or off-road excursions under the trees.

The 'Ultra White' lens comes with 16 per cent Visible Light Transmission (VLT), which is considered very dark and suitable for sunny days. The filter category is '3', this is on the safe side and good for use in the mountains. Some of the other colourways use different lenses, such as Smoke Mirror and Infrared. These have a higher VLT.

Donning the glasses with the Ultra White lens fitted for a summer's evening ride, they shielded my eyes from the sun and allowed me to pick out imperfections in the road surface. When the sun began to set and the atmosphere around me became darker, especially under trees, my vision was still good and I'd have no qualms over using these on slightly overcast days.

The clear lens provides a shield against road debris and suicidal insects when out in the woods testing gravel bikes.

The open design means there's no frame at the bottom of the lens, and my peripheral vision wasn't affected by the frame at either end. Koo has built in four vents along the top of the glasses, and stopping at lights I experienced no fogging - though I would expect some on cold or wet days (I've not found glasses that prevent this completely).

Build quality

At £199, these glasses are a considered purchase and you'd want them to be long lasting. They arrive in a large presentation box, with padded inserts for the spare lens as well as a fabric carry pouch and a lens wipe.

The case itself is very much an added luxury, but it measures 14 x 17 x 8cm. This works well for storing the glasses at home, but (outside of lockdown) I'm often packing a race bag for events and would rather a smaller hard case I could slip into my kit bag.

Breaking the replacement nose piece when swapping between the two options was also pretty unfortunate, and it was largely because I had to pull quite hard to get the frame's plastic holder to release the rubber. I also found initially that swapping the lenses required quite a bit of force, but once I'd done it a few times it became quite easy to do by accident.

Whilst I love the fit and lens clarity of these glasses, the build quality of the plastic frame doesn't quite mirror that of similarly priced options on the market.