Upper: surprisingly breathable with a great fit on top
Tim: Nothing very specific to say about the upper. I would say that everything works well for me without anything very amazing. While the mesh feels a bit thick I don’t experience overheating even when I run with a temperature over 30°Cee (86°F).
I feel comfortable in this shoe from the forefoot – where the space is large enough to avoid unpleasant contact – to the heel where I enjoy the softness of the heel collar added to maintain the heel. Nevertheless I know that I have quite a narrow heel and that if I feel myself comfortable and well maintained I would warn people with above-average heel size who could find this area not large enough. Keep in mind that Brooks offers a 2E width.
Ivan: I find the so-called ‘engineered air mesh’ upper very plush and pliable. Despite being on the thicker side, my feet did not feel too warm during any of the hot summer days around here. Usually I am not a fan of rather padded tongues and heel collars, but in this case it didn’t bother me and the padding felt both light and reasonably breathable.
The Glycerin 20 has a generous fit overall. Compared to other classic Brooks models, such as the Ghost and Adrenaline, I think it is a tad wider around the midfoot and personally I prefer a tighter lockdown. Those with higher arches will probably appreciate the generous fit around the midfoot though. Despite the roomy fit I did not experience heel slipping and the soft upper ensured a comfortable experience at any time.
Alex: I always heard a lot about Brooks’ fits. People like those fits because they are no-brainers and most of the time very comfortable and plush feelings come with them. Wasn’t Brooks even rated like the company with best fitting shoes overall a few years ago? This rings a bell but I cannot remember where I read about it now. Anyways! Like Tim and Ivan said, the upper looks and feels thick but it runs lighter and while not mega breathable, it does not become an oven in there either.