Arena Powerfin Pro Swim Fins*Recommend sizing up if on the border of a size. 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 motion and a more powerful downward leg kick. Training your legs vertically using Powerfin Pros for just a