Usually, subsectors contain between 2 and 8 systems, while some may have more or less than this, the average is 2-8. The size is generally governed by the range of available patrol ships. This means that there are vast numbers of systems and planet planets which are not within a subsector, being out of reach of patrols.

These regions are reffured referred to as frontier regions or inter-sections. They are more commonly referred to as wilderness zones, forbidden zones and empty space. They are often unsafe as no one will come to your a stricken vessels aid unless there is a passing battlefleet.

Inter-setions may contain gaseous clouds, dust nebulae, inaccessable areas, alien systems, unexploded unexplored systems and planets and uninhabitable worlds. These areas are sometimes found to be inhabiting by [[Rogue Trader]]s as they may well not have been explored by the [[Imperium]], and may contain materials or technology vital for the spread of humanity.