Marafast ATLFN05018BP 5/8-18 Gr.G Top Lock Flange Nut, Black Phos. & Oil Finish (Pack of 6)
Grade G Top Lock Flange Nuts. This lock nut has compressed threads at the top of the nut, creating a locking mechanism against the bolt. Top lock flange nuts are fastened or locked against a bolt without damaging the base surface.