A second group of distinguishing properties refers to their "composition". Networks of practice and formal work groups vary in terms of their "size" since networks of practice may range from a few select individuals to very large, open electronic networks consisting of thousands of participants while groups are generally smaller. They also vary in terms of "who can participate". Work groups and virtual teams typically consist of members who are formally designated and assigned. In contrast, networks of practice consist of volunteers without formal restrictions placed on membership.