Coastal Pet Tuff Collar Adjustable Harnesses are made of thick high quality nylon for extra strength durability and comfort and are specially processed to prevent fraying. All nylon products are carefully and neatly finished for the best look and durability. Measure around dog s body behind front legs for proper sizing. High quality nylon construction Processed to prevent fraying Finished for best color and durability FOR HARNESSES: Measure dog s girth behind front legs and add 2 for correct size.