Nose Cones are recommended on boats running in the 80 MPH range to enhance propeller efficiency and eliminate blow out. Propeller blow out is encountered when water separates from the gear case to the point where the distance is equal to or greater than the radius of the propeller MPH gains can be 2 to 6 MPH with the right propeller set up. Bravo castings are for 1990 and later. They come in either standard or low water pickup designs. Low water cones are used when running a high-X-dimension on high performance applications. All nose cone castings are 6063-T6 and molded to a glove like fit. This enables it to be installed with epoxy putty. Low water nose cones require a water passage to be machined in the lower unit (no external hoses). Does not fit Bravo 2 or 3 drives.