Only tried on and washed. This size is likely perfect for dogs weighing around 2.5 to 3.5 kg (5.5 to 7.7 lbs). Although it's labeled as size M, it's closer to a typical size S. I'm also selling a size up. It's in the style of Disney's Tigger and was super cute, so I bought a new size. I'd love for your dog to wear it, so I'm putting it up for sale.