vionic Prism sandals only wore once run small I'm more of a 10 1/2 and 10 usually fite in vionic (I have over 40pairs) but these seem to run a little smaller of you are a 9 1/2 true 10 they would work great. beautiful sandal with unbeatable comfort. Barely-there straps, metallic leather and beaded detailing combine for an event-worthy sandal that supports you at every step. Uppers: Leather. Footbed Lining: Man-Made. Heel Height:.63". Biomechanically designed to hug your arches, Vionic Technology helps support natural alignment from the ground up. Received APMA Seal of Acceptance.