We got a size M for Luna (6.8 lbs Chihuahua mix terrier). Got an email from Bao right after placing the order concerning if we have chosen the wrong size accidentally because Bao wears a small. She even let Bao try on a size M and sent us photos of how it looks on Bao, making sure that's what we want (Thanks for being so considerate!).
Size M is a little loose (as expected) but that's what we want because we want to layer it up with a shirt inside. We really love the material, it's thick and feels luxurious! Can't wait for Winter to come again later this year so Luna can go out and show off this jacket!