The HTP Elliptical Insert can only be used with the HTP Race Nozzle.  The Elliptical Insert increases thrust by removing the dead center core of a round stream of water and also speeds up the linear flow by design. This flow is extremely smooth all the way out to the end of the elliptical insert. This can give significant gains in speed and E.T. The elliptical configuration of the water stream also helps in adjusting the attitude of the boat.