This is the XS Scuba Standard Spring Straps Attaches to Most Brands of Large Post Fins Features: Attaches to most brands of large post" fins Comfort heel pad has a large finger loop, which allows easy on/off, even with thick gloves Stronger than traditional rubber straps No tightening or adjustments needed Passivated 304 stainless spring will not rust Internal safety line prevents over-stretching How to select the proper size Spring Straps? Insert your foot into the fin pocket while wearing a boot Measure from the attachment point on one side of the fin, around your heel, to the other side Choose the spring straps with an overall length that is approximately 1 inch shorter than this measured distance The Standard Spring Straps are a great option to upgrade your fins standard straps."