25 mm thickness. First, the bottom of the slippers is quite heavy and uncomfortable, due to being made up of a sack of millet. The foil attachment is perfect for the upper lip and face if you have a bit of dark hair there. He likes them and they look good. The material is just disappointing. Maybe some people like that, but they dont sound natural or balanced to me. Got the glow in the dark because all my bags and my car interior are black. The color is so bright! 5 in running shoes, and the UGG 9 is spot on. I have owned Spenco inserts before and SuperFeet so the feeling of support is the same as the inserts.