Oceanic USA Viper Full Foot Diving Fin Flexible Power Thrust Channel directs water off the tip of the blade for improved power and efficiency Power Vents reduce stress while accelerating water over the blade Oversized blade produces increased thrust and propulsion Generous yet streamlined foot pocket fits a wide range of boot styles while significantly reducing drag Extremely lightweight for increased performance and ease of travel; 3 - 4 Men's US shoe sizes/4 - 5 Women's US shoe sizes