Castle NutThis marine grade brass castle nut is built for inboard prop shafts with a 1" to 1 1 8" diameter using 3 4" 10 thread pitch, a standard on many Malibu and Axis boats. Its castellated design allows a cotter pin to lock the nut in place, preventing vibration related loosening and securing your propeller to the shaft. Machined to precise standards and resistant to corrosion, this nut is essential for propeller retention in both salt and freshwater