arena's Powerfin Pro II Training Fins are the fins all expert 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. With a short blade for maximum forward thrust, the open heel ensures maximum ankle flexibility, optimal stability and comfort. These high-quality swim fins are also equipped with special notches on the bottom ribs for faster kicks and side grooves for better control. Left and right fins are shaped individually. The soft silicone material provides maximum comfort and a reduced chance of blisters. PVC free. Training your legs vertically using Powerfin Pro II swim fins 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 to make sure you are performing a proper leg kick. Refer to size chart for the best fit.