In the world of model aircraft there are several competition classes to signify engine displacement.

Class Cubic Inches Cubic Centimeters 1/2A 0.000 - 0.050 0.000 - 0.819 A 0.051 - 0.1525 0.835 - 2.499 B 0.1526 - 0.300 2.500 - 4.916 C 0.301 - 0.650 4.932 - 10.65 FAI max 1.526 max 25 Jet