The "Chuckit" ball launcher has been a godsend and probably has saved my dog from injury on a number of occasions. Sounds like an odd testimony indeed, but I have a very sociable and trusting whippet and whippets are possibly one of the two fastest dogs on the planet.  Before Jack was interested in chasing a ball, he would only want to entice dogs to chase him at the dog beach or dog park. Consequently, there have been dogs who became aggressive during the chase and have lain in wait for him to run by and have nipped and toppled him to get him under control.  I realize this had to stop.  So I bought a Chuckit and Jack was hooked immediately.  Now he could care less about dogs chasing him - he is happy to greet them - but he does NOT want to be chased any longer.  He is so addicted and hyperfocused on the ball.  And IF a dog at the beach or park starts chasing him once I have "chucked" the ball, when the dog catches up with Jack, he just comes to a dead stop and will not let the dog chase him.  Additionally, in two instances recently, I was able to use my chuck it to ward off dogs rushing towards us, off leash, with no owner in sight.  They stayed clear of the crazy lady with the orange stick!  So, it has been miraculous for us.  Jack's brother is NOT interested in the ball and he has already had surgery for a serious dog attack - dogs chasing whippets - whippets with very thin skin and skin tears easily.  I love my Chuckit launcher.  But I ONLY buy the ULTRA balls which are orange rubber with a blue contrasting stripe because they bounce so nicely.