The Flex trainer by Freet is made from a breathable & durable re-cycled BottleYarn, with a TPU overlay for added protection. This lace up trainer has a MultiGrip performance zero drop outsole, making it suitable for both light trail & everyday wear. The overall stack height is 7.5mm with the insole and 5mm without as the thin & flexible 2.5mm insole is removable for those who want a more barefoot feel.