We used to have a pack of small, medium, and large.
Now we just have medium large.
:-)
My wife and her friend took him out for 9 miles of running today on the mountain bike trails... he's a full on athlete. When he came home he chased the squirrels back in to their trees and then instigated a wrestling match with me.
The best part is that he hangs with my wife and doesn't get distracted by the hunting dogs, the deer parts, or the other people she sees out there. He sticks by her side and know what his job is.
If there is anything fun to do out by the gate he doesn't hesitate to fly out the window or door and go see what's up.
:-)