A liquid drug transfer device that includes a vial adapter having at least two non-adjacent vial retention flex members and at least two non-adjacent vial guidance flex members. The vial guidance flex members are each provisioned with a purpose design hinged zone distanced from a vial adapter top wall for intentionally being hinged thereat on telescopic snap fitting on an injection vial. The vial retention flex members can double as vial guidance flex members with the condition that their hinged zones are distal to their inwardly protruding vial retention ribs relative to the vial adapter top wall.