Good morning, Thank you for your message.  I checked with our graders on this and there is no quantified measurements for these terms but generally speaking a small split would be around 1" or less, a medium split would be around 1" to 4" and a large split could be up to the entire length of the spine. A fully split spine, however, would be noted as such on the label.  Please be aware that these are just generalizations and you may find some examples that differ in length slightly.   I