A total must have if your dog likes to play fetch.  The adults and 12 year old son use the longer Chuckit and my 8 year old daughter prefers the 12M size.  I'm a terrible thrower and playing fetch with my fetch crazed dogs would be an exercise in frustration without the Chuckit.  I find it much easier to control my aim using this.  Did I mention I'm a terrible thrower?  I'm actually pretty decent when I use the Chuckit. They're awesome.