The Mountaineer Chest Compression Adjustable Reflective Easy Pull Dog Harness is composed of Durable Nylon with dual front and back reflective lining for night protection. This Pet Harness places pressure on the Dogs chest bone rather the neck or stomach area providing superior comfortability and Lighter Compression for your Dog when tugging. This Harnesses features reflective lining across the front and back and is fully adjustable. Sizing Measurements L x W (Height adjusts) SMALL - 7.9 x 2.8 MEDIUM - 9.8 x 3.2 LARGE - 11.6 x 3.8