Families not only have boundaries between different family members or subsystems (internal boundaries), but also have boundaries with the outside world (external boundaries). Such boundaries refer to the degree of influence, time, and information given to people outside the family. For example, families with few relationships outside the immediate family have rigid external boundaries. Those who have too many people flowing in and out of their home, or who let non-family members unduly influence their family life have overly porous boundaries. Optimally, families should have firm but permeable boundaries so that there are strong and positive relationships with people outside the family, but clear distinctions between those who do and do not belong to the family system.