The large harness fits a 19"-23" chest and an 13"-15" neck. Collars can put a real strain on your pet's neck and shoulders, especially if they tend to pull. Harnesses redistribute the weight over the chest and back to avoid eventual health issues from collars. But your dog doesn't deserve just any harness. They deserve something lightweight and comfortable that breathes, especially in the summer when the weather's perfect for longer walks. This harness is made of polyester air mesh that allows air flow while still providing all the benefits of a harness, and it has a soft filler that promotes superior comfort for your pet. It secures in place with a snap buckle and an adjustable velcro closure to create a fit that's just right.