Castel Nut Fine Thread Zinc Plated 3/4-16 Grade 2

Also known as castle   nuts,  secure these nuts by inserting a cotter pin or safety wire through the slots and a drilled hole in your bolt for mild loosening   resistance.  They’re not recommended for use on parts exposed to high vibration because the pin is prone to shearing under prolonged   stress.  Height includes the   slots. Cotter pins are not   included.  A Zinc-plated steel provides corrosion resistance in wet   environments.