The Express ADJ fin represents the latest in technology and material innovation. Comfort, power and efficiency are the hallmarks of this propulsion machine. Strap a pair on and see for yourself. The Express fin works on the same principle as the popular Slingshot and Hotshot fins. The function of the Slingshot power bands has been converted into the Express ?Armadillo?. This patented, elongated membrane is made from ultra-elastic rubber. Like power bands, it accumulates elastic energy during the down stroke and returns it at the end of each kick cycle.The Armadillo also bridges the gap between the front of the foot pocket and the back of the blade, which eliminates any water transfer through the fin.The blade connects halfway back on the foot pocket at the Mid-Foot Flex Joint. This eliminates hyper-extension of the toes and ankles.The foot pocket is not only comfortable, but provides different thickness zones which properly secure the foot to the blade for maximum energy transfer