Adjusting the EzyDog Harness We ordered a medium for Roy based on the Ezydog size guide (below), but at first we were worried it would be too small. Little did we know that the harness is fully adjustable so that it's the perfect fit every time. To adjust simply slide the branded neoprene scratch protector to one side, which then reveals the adjustable chest strap. Remove and adjust the Velcro so that its at the maximum recommended width for strength which is shown my the red strip. It will take a few adjustments until you have find the perfect fit for your dog, remembering that you need to be able to fit 2 fingers between the harness and your pooch.