An A grade starport is equipped to handle ships and cargo of almost any conceivable kind. Many mechanics, architects and spare parts shops can be found aboard the station, making it a favoured stop for ships in the area.
A B grade starport is equipped to handle most ships and cargo. Although fully equipped, it is of a lower quality overall than a type A, but is also cheaper to dock and repair at.
A C grade starport can only service small craft (Under 100 tons), and can repair and service them. Unfortunately, they only sell unrefined fuel.
A D grade starport has few amenities beyond a handyman and fuel reserves.