Silicone. Size EU 40-41, USA 8-9, UK/AUS 6.5-7.5. Original $80. These are the fins all professional swimmers have been waiting for Their innovative design features a sloping surface and hydrodynamic slits in the top to allow you to swim with a faster leg kick and better control The open heel ensures the best possible ankle flexibility allowing faster upwards notion and a more powerful downward leg kick Training your legs vertically using Powerfin Pros for just a few minutes today will help you improve your underwater phase The vertical leg kick allows you both to control your body position and make sure you are performing a proper leg kick x listed on Mercari for more shipping options