The simplest way to figure out whether a PTO is North American or metric is to determine the shape of the tubing and shafting. A PTO is domestic if the tubing/shafting is square, rectangle, hex or splined. If the tubing/shafting is bell, lemon, or star-shaped, then it is metric. There are two types of metric drive lines: German style (Walterscheid) and Italian style (Bondioli & Pavesi). The German style shafting has lemon and star profiles while the Italian has a bell shaped or 4 lobed design.