Some of the most common metric circular connectors are the M8 and M12 style variant. The M standard for metric and the latter number defines the locking thread size. Thus, an M8 connector has an 8 mm locking thread while an M12 connector has a 12 mm locking thread. The range of metric circular connectivity can be grouped into three categories – field installable connectors, receptacles and cable assemblies. Field installable connectors are male or female plugs that can be assembled in field with or without tooling. Receptacles are the panel mount jacks which can also be field installed or have leads attached. Additionally, fully assembled overmolded or non-overmolded cable assemblies are commonly available for sale. These cable assemblies are offered in standard lengths, but custom lengths are possible as well.