Measurements are from buckle to buckle, you will need to allow an extra 1" compared to your normal girth size because of the fleece liner.
For horses with mostly short backs and wide ribcages and/ or narrow chest. The girths slide forward. The crescent girth shape gives room for the bulk of the rib cage and belly. So the girth does not push forward.
Attention: There is a label with direction indicator. Always place the girth according to the label.