A nozzle for forming a container preform into a plastic container, the nozzle comprising: a nozzle body (260); and a sealing portion (272) configured to engage with a stepped interior of a finish portion (164) of a preform (160) having a longitudinal axis to seal without the use of an O-ring, wherein the nozzle body further includes a tip (280) comprising a narrowing portion of the nozzle body forward of the sealing portion so as to provide clearance of the nozzle body from an interior surface of the finish portion.