Hi. I have a beautiful adult chihuahua x mini foxy girl. Ive had difficulty buying a harness that fits her comfortably, especially without the buckles being under her armpits causing discomfort, even pain (some designers clearly dont think of this). Over the years Ive bought numerous harnesses, all with comfort/fitting problems, so I bought this not expecting much. It has however turned out to be the best one of all. I bought the smallest one and had to adjust it to its absolute smallest size to accomodate her, shes around 4kgs, so if you have a dog under that it may be too big, but overall Im very happy, but more importantly, she is. Would highly recommend.