"We now have two collars for this system, becuase the first worked so well!
Our little escape artist was able to get out of collars and harnesses and, despite our efforts, she kept running out into the woods and getting hurt! After two surgeries (and almost losing her eye!), we gave in and bought her her own collar. Now when we put her out, she's still in our yard when we go out to get her... and, she hasn't been able to take it off!
I have to admit I was a little scared about putting it on such a little dog, but she's just fine. We've just used two different settings. Our Lab's collar is set on 5, and the Pug/Chihuahua is set to 2 (1 is sound only). The radio unit works equally well for them both!
(The pictures give you an idea of the size difference of the dogs. the collars are the same size (one's just shorter)."