Innotek UltraSmart Extra Collar Receiver for IUT-300 Dog-Training System,  IUT-011 Extra collar receiver for IUT-300 dog-training system Train a second dog with 1 system; 300-yard range Comfortable collar fits neck sizes 8 to 24 inches Delivers 9 levels of electronic stimulus dogs find undesirable Receiver measures 2-3/4 by 3/4 by 1-1/4 inches; limited lifetime warranty