The Trixie TopTrainer training harness in black helps to hold the dog without much effort. Light impulses can interrupt eye contact with another animal or object. The training harness is intended for education and should not be used continuously. An instruction manual for the proper use of the training harness is included. To determine the correct size, take a measuring tape and measure around the snout and neck. The training harness should not fit too tightly. There should be enough space for a finger under the measuring tape. It is better to be a little too loose than too tight.