Looking at the Octal mips a medium fits 54-59 cm and large 56-62 cm. I’m 58 cm. Anyone else in between sizes like this? Is it better to go up or down for a good fit?
The inside of either will fit you, but you’ll have more of a “mushroom head” with the bigger one. I don’t mean that as an insult, some people love that big POC helmet look. The only other thing I’d consider is how much room you may need for something like a winter hat and if that 1cm is enough (it probably is).
I’ve got a ~59-59.5cm head, but I have a large POC Ventral Air. I tried the medium and it did not fit at all.
It’ll also depend on your head shape. From my experience, POC helmets tend to fit oval shaped heads better than round heads. If you’ve got a round head, you’ll feel pressure on your temples and/or sides of your head. For what it’s worth, I’ve found they slightly tweaked the fit on the newer models to accommodate both head shapes.
On the note about having a mushroom head - POC helmets tend to have this look (for better or worse). Related to my comment about older (Octal) vs. newer (Ventral Air) models, the newer models are slightly less mushroomy than the older models.
I’ve now decided to buy a Kask Mojito3
I am also 59cm and M fits me well. As you say, it’s quite individual
between sizes? They almost fully overlap.
Get the smaller one unless if you wear hats a lot.