There are four different ship sizes: small, medium, large, and huge.
A small ship uses a plastic base that is about 1-9/16" (4 cm) long. The rules of X-Wing are written for small ships and therefore there are no special exceptions for small ships.
A medium ship uses a plastic base that is about 2-3/8" (6 cm) long. Medium ships have the following exceptions:
A large ship uses a plastic base that is about 3-1/8" (8 cm) long. Large ships have the following exceptions:
A huge ship uses more than one plastic base. Huge ships have many additional rules. They were introduced in the first edition of X-Wing and will be reintroduced in an upcoming product.