The Winnwell Goalie 6 oz Training Ice Hockey Puck is designed to enhance a goalie's reaction time and hand-eye coordination, as the white puck makes it much harder to track. By training your eyes to track a white puck that is difficult to see, it'll become much easier to track and save a black puck come game time! It's designed with regulation size and weight so when you train with it, it performs just like an official game ice hockey puck.