Duchess wouldn't be able to back out of the K9 harness because it goes over the head, with the Velcro strap going across the chest, and then the buckle strap does up under the tummy. It's very easy to put on and take off, but is very secure. My guys were able to walk out of other harnesses I've tried in the past, but they have never been able to get out of the K9 Harness.
