He is trained on the Tritronics sport 60.He knows all the commands,and when I'm not around the yard he feels its time to leave! The wife and I are considering invisble fencing but are relocating in 6-8 months. I guess for now I will always have the collar on. He is a very head strong dog,and sometimes seems to do things (commands) reluctantly,and I don't think I can ever change this in him. Any tips on his sporadic aggression? :twisted: