Bmac, spend the money and get the best (Tri Tronics). The petsmart collars are junk and don't give enough correction to stop the problem.
Also suggest strapping it on tight enough to work (prongs must be tight to skin for them to feel the burn). These use a cr2 lithium battery and I have had some last for 6 months with plenty of juice. 5 levels allow you to find just the right one without making the dog $hit when it goes off. Makes my nights a whole lot mo peaceful knowing everyone is quiet.
