The most common layout was two crankshafts, with the crankshafts geared together (in either the same direction or opposing directions). The Koreyvo, Jumo, and Napier Deltic engines used one piston per cylinder to expose an intake port, and the other to expose an exhaust port. Each piston is referred to as either an intake piston or an exhaust piston, depending on its function in this regard. This layout gives superior scavenging, as gas flow through the cylinder is axial rather than radial, and simplifies design of the piston crowns. In the Jumo 205 and its variants, the upper crankshaft serves the exhaust pistons, and the lower crankshaft the intake pistons. In designs using multiple cylinder banks, each big end bearing serves one inlet and one exhaust piston, using a forked connecting rod for the exhaust piston.