Abstract: The present invention is a multiport cofinger as well as a device that includes a multiport cofinger stopper and a microreactor. The stopper includes a main housing with a central orifice and a plurality of outer orifices located about the central orifice, and a sealing mechanism on the sidewall of the main housing. The cofinger is a concentric set of two tubes, but not necessarily symmetrically concentric. The cofinger has at least one inside tube and an outside tube; and each of the tubes has an upper end and a lower end, the lower end of which may be closed or open. The sealing mechanism maybe a tapering of the sidewall of the main housing to permit force fitting thereof into an opening of the microreactor or it may be designed for external stopper connection. Alternatively, there is at least one O-ring located about the sidewall of the main housing. In some embodiments, the main housing has an upper section and a lower section, with the lower section of smaller diameter than the upper section.