The Ultra Flex Bootie is built on the legacy of Sea to Summit's original, low profile, sensitive Flex Bootie. The fit has been improved with an updated last shape and an added, secure velcro closure system, whilst retaining the high sensitivity that makes this bootie a favourite. Stitching lines have been optimised to prevent chaffing from foot straps. The rubber laminated sole gives all the protection you need while also maintaining the best flex for ultimate comfort.