The Limited Slip style collar design has a tug that pulls from one side only. It can be adjusted for size to be LARGER than the ordered size but cannot be made smaller than the size ordered. The Limited Slip style can be ordered with and without a buckle. If you order it without a buckle, be sure that the collar will slide over the widest part of the dog’s head. All slip style (limited slip, martingale, etc.) collars should be measured the same way that you would measure for a prong collar. See the video here for how to measure.