most all the brands have probes long enough. they only have to be about a 1/2 inch long for long hair and about a 1/4 inch long for short hair. we use the long ones for the lab and we grind the probes down to about a 1/4 inch for our beagles so that sticks cannot get up under the collar. just brush the hair forward a bit to get the probes down to the skin. also the collar has to be tight on the dog or it will not work.