I have a Labrador Retriever that LIVES to retrieve.  If I didn't have this Chuck It I would never be able to use up his energy.  My dog sprints about 100 meters a time on his retrieves because of the Chuck It.  He has built up his endurance and can go for close to an hour everyday now.  When we started it was 15 minutes every third day.  I have the Chuck It glow in the dark ball and agility ball and both are amazing products.  The stand up to heavy chewing and allow us to play even when the sun goes down.