I have worked with this collar consistently for over 30 years.  It is the safest and most effective piece of training equipment I have found in that it is silent, light weight, and sits well above the trachea.  The use of this collar is mandatory in all of my obedience classes and   one is provided for each Basic Obedience student that enrolls in my classes.  I discuss this collar at length in the Orientation class for Basic Obedience.

Collar Fitting Instructions

This collar has one stationary ring, one floating or loose ring, and a snap.

This is the correct placement of this collar.

Place the fabric portion of the collar under the dog's chin.

Have the rings under the dog's left ear and the snap under the dog's right ear.

Attach snap to the floating or loose ring.

Attach leash to the stationary ring.