Class A: Small Rocky Planetoid - Similar to Pluto
Class D: Planetoid, moon or asteroid. Examples include Regula and Rura Penthe.
Class B: Small Rocky Planetoid - Similar to Venus
Class M: Earth-like both in its size, core, and age as well as in the advancement of the native creatures. Class M worlds are frequently the home of sapient races capable of traveling in space.
This is the main planet of occupation. Girin live here for the most part.
Class L: Habitable planet that supports primitive life. This can be very simple fauna, or even life as advanced as a Bronze Age culture.
Class S: Largest designation for gas giant. Ultra giant, not suitable for Iffens.