Zack & Zoey I'm Not a Pony Dog Tee, Small/Medium, Brown Size Small/Medium is a half-size between a Small and a Medium. It fits dogs that measure 10"-14" from neck to butt; 11"-15" neck; 14"-17" chest (Small dogs = 12" long & Medium dogs = 16" long). PLEASE MEASURE YOUR DOG BEFORE YOU BUY. Dog garments come in 10 different sizes. High Cut For Potty Time Machine Washable