This particular harness is made of a simple black elastic, with silver tone metal clasps and a silver tone metal ring at the back. Since the harness is made of elastic it will fit quite a few people, however I'm calling this one a small/medium. The elastic measures 26" around the ribcage, unstretched, and will stretch comfortably up to 30". If you need the fit to be tighter, let me know as this is a fairly easy adjustment to make. If you need a larger size shoot me a convo, I'm always open to making custom sizes, equal fashion for all!