Proper fit is critical to the performance and effectiveness of the SCOUTBARK100. If the fit is too loose, the Pet Collar Unit will not be able to get sufficient contact with the skin to detect barking and deliver static correction. If the fit is too tight, it will irritate your dog’s skin. Tighten the Pet Collar Unit high on your dog’s neck, tight enough that you can get two fingers between the collar strap and your dog. It should not be able to rotate around the neck.