The Scionon® Round Caliper Guage is included with each Graft Crafter® unit, but extras can be purchased separately. The Round Caliper is in “English” inches for us non-metric types. These rules are used to grade rootstocks and scionwood into similar sizes for easier grafting. They are also useful for grading nursery stock and trees. A long straight ruler calibrated in metric is also available on special order in metric.