We have had a ton of these.  They are great for big dogs with lots of energy.  It takes zero effort to launch the ball 50+ yards.  The BEST part is you don't ever have to touch a slimey ball.  Have the dog drop it, and then the chuck it just "clicks" right over the ball and you are ready to go.  That feature might be even better than my dog being tired after 10 or so throws!