K7 Hydrogrip Water Polo Ball- NCAA, NFHS, FINA, USA Water Polo Approved. Kap7 has tapped into years of experience, proprietary technology and the highest quality materials to develop the HydroGrip into the best and longest lasting water polo ball in the world. The HydroGrip has been designed to meet guidelines for local, national and global specifications. Kap7 HydroGrip balls are all made to the exact specifications whether for NCAA, NFHS, FINA or Club water polo. Size 5 - Official water polo ball size for the high school boys and NCAA and International Men players. The KAP7 size 5 HydroGrip Water Polo Ball has quickly become the go to choice from amateur to elite water polo players.