The Dura Outdoor Pickleballs, also known as the Dura Fast 40, are a seamless one-piece rotationally molded ball specially designed for pickleball. They, like all outdoor pickleballs, have thick walls. The purpose of using hard plastic for a pickleball is to increase the life span of the ball in rough outdoor conditions. The name of the ball is short for “durable” and these balls live up to their name.