IST Stainless Steel Coil Fin Strap w/FB7 Buckles (Pair) Rust resistant stainless steel spring straps are ideal for technical and recreational diving. The main advantage to these straps are that when fitted, fins become easier to put on and take off. There are 3 different lengths to choose from. Sizing - Approximate Spring Length Small: 17.1cm (6 3/4") Medium: 19cm (7 1/2") Large: 21cm (8 1/4") X-Large: 22.8cm (9")