Harnesses are adjustable around both the neck (A) and chest (B). Kwik Klip buckles allow harness to be fitted and removed quickly. These comfortable harnesses can grown with the dog. Adjustable straps: Extra Small (A) 9-15" (B) 7-11", Small (A) 13-21" (B) 9-14", Medium (A) 17-29" (B) 12-18", Large (A) 22-38" (B) 16-26".