Hello David, Thank you for your inquiry! Check the fins you own against the tins on our site, then choose the size fin with the option of ordering the spring straps. Using that method will select the correct size Spring Strap.
http://www.scuba.com/scuba-gear-113/012068/Innovative-Ez-Spring-Fin-Strap-Pair.html If you would like to place an order or have questions about our products, please contact one of our certified Dive Instructors at SCUBA.com by calling 800-247-2822 <> 949-221-9300 or e-mail us at: info@scuba.com