Mares X-Stream Fins are an adjustable, lightweight, open footed fin with a new foot pocket and new blade construction. Please note that open heel fins are designed to be used with boots, the style/thickness of your boot may affect the size of the fin, so please keep in mind that thicker boots and those with molded soles may require you to size up. Not sure about sizing? Contact us and we'd be happy to help! *Closeout Item- Due to the age of the stock, there may be some yellowing/discoloration, this is purely cosmetic and does not affect the performance of the fins.