Our dog is approx 25lb (11.4 kg) with lean and somewhat long torso. The body buckle is adjusted to the tightest because of her slim body. The body belt/buckle fits her perfect at the moment, no sagging of the belt in a circumference. If our dog loses some weight and becomes even more slim, the body belt/buckle might become too loose (we already tried XS-long and that was too tight on our dog). Before purchasing, we searched and googled all over the internet but could not find a decent video/images on a dog by the actual user. Here is Hagihara Harness on our dog. https://youtu.be/5cvqw9CLq6c