SIZE AND FIT: For back length, measure from the base of neck to the base of the tail. 12 inches long = Size 12. For dogs with larger than normal chests, double check their size by measuring all the way around the dog under their legs to their upper back for their chest girth measurement. You may need to go up or down, based on their chest girth. Reference our size chart or reach out for help. Water-resistant exterior so your pooch stays dry Side zipper closure for easy pull-on comfort Adjustable neck for the perfect fit Full body protection like never before