Sized stations are NPC owned stations that are of a smaller size than regular stations. The result is they can only be docked at by correspondingly smaller ships, i.e. (VS) Shuttles, Ventures and Frigates - (S) Destroyers, Industrials - (M) Cruisers. They may or may not have smaller markets for items of definitive sizes or price ranges and under.
A variation of this theme may be secret stations, i.e. stations you can only find in one or two ways, i.e. you are taken to them through a mission arc, or another player physically shares the information about these station. They can not be landmarked, as any landmark in a “several” 1000km radius from these stations fails. Once visited they show up on a player map.
These stations might offer unique/exotic services and/or products.