Answer I wear a women's Size 9.5. My athletic shoes fit into this bag, albeit quite snugly. I'm pretty sure it wouldn't accommodate a men's shoe larger than a Size 8.
I think Eagle Creek has a larger-sized shoe bag that's more suitable for men. You might want to consider purchasing that instead.
According to information listed under the first bullet point under the product overview tab:
Fits shoes up to men's size 8, women's size 9.5 and EU size 41