These are the two key areas that will affect comfort the most.

The nose bridge will, in almost all cases, come with some kind of rubberised or soft touch cover to both help the glasses stay in place and also prevent the plastic underneath from rubbing on your nose.

Whether the nose bridge is built in or replaceable will, again, probably depend on how expensive the glasses are. Oakley, for example, have a fully replaceable bridge and their performance glasses come with a spare in the hard case. But they’ll set you back a fair amount.

Stating the obvious, though, everybody’s nose is different and what works for one person won’t necessarily work for everyone else, so trying on a set of glasses in your local bike before you buy is advised. Any aspects of the fit that might seem slightly off on first go (slightly tight or wide on the nose, a little too much pressure from the arms on the side of the head) is worth noting as it’ll seem much more irritating over the course of a long ride.

The tightness of the arms is something to be aware of as well. Personally I’ve found that just above my ears is where tight glasses can become painful on rides over 90 minutes, so I have to make sure that any eyewear I buy is no tighter than it needs to be to keep them on my head around that area.

Another important feature of the arms is length. And, more specifically, how the length of the glasses interacts with the retention system of your helmet. In the past, I’ve found that the long arms on Oakleys and the fairly extensive retention system on Kask helmets don’t always work well together, and the overlap of the arms on the bottom corners of the system throws the fit of the glasses off quite a bit. The obvious solution to this problem is to chop a bit off the arms, but if you’re happy taking a knife to an expensive set of sunglasses, you’re significantly braver than me! As a side note, Oakley’s new Jawbreaker glasses have adjustable arms, with three length settings.

Also, most sunglasses have some kind of grip system on the arms to help them stay in place. That ranges from rubber sleeves that cover one section all the way down to grippy little tabs at the end. They also add a bit of comfort over plain plastic too. To be honest, it’s not worth getting too worried about grippers, because it’s the fit of the glasses and not the grippers that will play the biggest part in making sure that they stay in place.

Getting the balance right between a fit that’ll work and one that’s too tight/loose can be a tricky one if you’re buying your first set of bike-specific sunglasses. It’s amazing how something that doesn’t feel too bad when you’ve only had the glasses on for a few minutes can be magnified ten times after a couple of hours on the road.