One is the discomforting but not harmful high frequency sound (20,000Hz-25,000Hz), audible to dogs but not to humans. And, the second is a super bright LED flashing strobe that temporarily blinds and confuses the dog.
Dimensions: 4-3/4 x 1-3/4 x 3/4
Helps stop the approach of unwanted dogs up to 40 feet. Also has a training setting. Can be used as a flashlight.
Requires one 9 volt battery (not included)