A 4.3/10 coaxial connector configured to receive a mating 4.3/10 connector includes: an inner contact; a dielectric spacer: and an outer contact, the dielectric spacer separating the inner contact and the outer contact. The outer contact includes an outer wall and a plurality of spring fingers, the spring fingers configured to deflect radially inwardly when the mating 4.3/10 connector is mated. The connector further comprises blocking structure that prevents mating of a Mini-Din connector.