The Primus outsole is around 2mm thick. It's a night and day difference compared to a normal shoe. I actually think the whole "we need arch support argument" is sorta overblown because I have super high arches and had issues with my feet pronating in, putting stress on my knees, and since I've swapped things got much better. You change how you walk, so you don't slam your heels down like most do, instead relying much more on Achilles and calf muscles. My foot fascia feels stronger as do my calves after daily walking in vivos, and this was noticeable a few months after swapping. The first week was the most odd, as you somewhat have to learn how to walk to not have as much impact (let your calves be the "spring" and land midfoot or ball of foot) especially on things like concrete.