Spindrift Step-In Dog Harness Size guide: XX-Small-(5/8" x 11-14"), X-Small-(5/8" x 13-17"), Small-(3/4" x 15-21"), Medium-(3/4" x 20-32"), Large-(3/4" x 28-40") Sizing - Harness sizing measured around dog's rib cage, behind front legs Spindrifts Step-in Harness is an easy and comfortable way to walk your dog and is a great solution for the spirited dogs who like to pull or slip their collar over their head Easy - lay the harness on the ground, have your dog step in, pull the harness up, clip the buckle and youre ready to go A double ring closure means there is no load on the buckle for extra security even for the strongest pullers