Chubby, buff, tiny, stringbean, bigbones, scrawny or petit; I could keep going, because no one is the same, but remember everyone fits a great accessory.
All the sizes are in un-stretched measurements, which means that because most items are made in a super soft jersey, that they can easily stretch about an inch more than the actual measurement listed, Tween and Teen can often stretch quite a bit more.
Micro: 32 cm or 13 inches.
Mini: 40-43 cm or 17-17 inches (Earflap hats tend to lean in the higher range).
Tween: 48 cm or 19 inches.
Teen: 51 cm or 20 inches (Teen hats can also be worn by adults, because of the stretch).
One-size: One size fits most. Fx. Headbands are listed as one-size, because the knotbow can either be tied bigger or smaller.
The smallest leggings size is 80 (6-12M) and the biggest is 110 (about 4-5Y). From experience, the smallest of the legging can easily be used for a smaller Ranger than 80.