This unit delivers a mild shock. Each family member felt the shock before being able to use the control unit on our dog. The shock is equal to a strong static electricity shock that you might get at the mall when you touch one of the metal clothing racks after walking on a nylon commercial rug. It is startling, but not hurtful. Our dog is a beagle mix, and she likes to ignore us when we call, would try to run off into the woods, and wouldn't listen unless she wanted to. Our previous pets had never exhibited this level of stubborness, so this was the first time we had considered a training collar. You train the dog by giving the command, then a vibration if the command isn't followed. Repeat. If the dog still ignores you, then give the command followed by a shock. We found that our dog initially responded well to the vibration, but over the course of a month she began to ignore the shocks if she really wanted to. When called, she would eventually come, but it might take 3 vibrations and 3 shocks before she decided to come when called. So the dog does get used to the vibrations and shocks, if the dog is really stubborn.
The pro is that the batteries are easy to get (9V and AAA batteries). The collar never did turn off, even when the unit said it would turn off when the dog was asleep or otherwise still. The batteries would die in less than a week in the collar. The remote unit batteries last longer, since you can manually turn off the remote when you don't need to train the dog. This appears to be a common problem with training collars, so the easy-to-get battery types was a huge plus. Some other units use odd battery sizes that are only available online.
The con is that the antenna is very fragile, and it broke in less than a month. We opened up the unit and found that the antenna was attached by a tiny solder point to the circuit board. And once the antenna broke away from the board, then the unit no longer transmitted the shock or vibration (although the flashlight and whistle part still worked). Based on how the antenna is connected to the unit, it will break quickly if you raise and lower the antenna a few times. We thought we would try to re-attach the antennae, but that didn't work.
This was the first training collar unit that we purchased, as I did not want to purchase a more expensive unit only to find out that our dog did not respond to the collar. Our dog, after realizing that the unit no longer functions, is starting to revert back to her old ways. So realize that some smarter dogs may figure out the collar, and if the batteries die, then the dog will again become stubborn. This is similar to dogs who learn that once they cross an invisible or electric fence, then there are no more shocks to worry about.