Unlock: Cargo Bay

Unlock: Cargo Bay is a Cartel Market unlock which grants an additional cargo hold bay.

Source
Unlock: Cargo Bay can be purchased from the Cartel Market for cartel 475 for the current character or for cartel 1,050 for all characters on an account. This unlock can also be accessed from the cargo bay window and can be purchased for the current character for credit 40,000 if you are a subscriber.