My 3 year old Springer is a tennis ball nut!  There's nothing she loves more than her tennis balls except maybe chasing them - practice for catching the squirrels on our property!  This Chuckit is easy to use and once you get the hang of it you can pitch a ball a long distance saving on elbows and shoulders.  Any tennis ball will work in the head of the device.  The best way to lob a ball a goodly distance is to NOT insert the ball all the way into the head.  Place the ball about half way in, just enough so it doesn't fall out, take a standing or sitting position, and swing your arm up from a ground pointing position to just head level and let fly!  Pretend you are a kid again and swing your arm like a windmill.  Just stop the motion when your arm is pointing straight towards the heavens.  The ball will launch at least 50-80 feet in an arch.  Great invention and I love it and my dog loves it.  In all fairness to anyone who isn't finding it easy to use, well, neither has my husband been overly successful at using it either but then he's not very coordinated, LOL!  Such a simple device and I only wish I had thought of it.  Buy it and your dog will love you forever and you won't suffer any more shoulder pain pitching those balls for that slobbering ball of fur you own.  Enjoy!