Petrainer IS-PET998D2 330 yd Remote Dog Training E-Collar for Small/Medium/Large Dogs, 6.69 by 1.96 by 5.39" 300m remote control electric shock devices for 2 dogs with big LCD Display Dog training collar with 4 modes: static shock/ vibration/ beep/ light Provides a professional 100 level shock and Vibration . Over 3000 different identity codes to prevent conflicts with other e-collars Saving beads switch inside will ring if you shake the receiver. Every time you put out the battery, you need to match code again