Small and powerful. Fits All Dogs. Collar is adjustable from 10" to 24". Collar has patent pending internal antenna system. Digital technology maximizes power, minimizes frequency interference from other devices. Continuous stimulation and Positive Vibration simultaneously; momentary "nick" stimulation. Allows handler the option to vibrate instead of shocking to make training connection. Compact transmitter antenna, 3/8"x1"x2", fits keyring, necklace or lanyard. Retractable transmitter antenna gives 250 yard range. 8 different levels of intensity with push button adjustability. Waterproof collar, 1-1/4"x1"x1-7/8", has patent pending built-in magnetic on/off system. Collar clip on/off. Replaceable collar battery, alkaline or lithium 6-volt. Transmitter battery 3-volt watch style. Unit Includes one collar, one transmitter, one tester, batteries & training book.