5/8"-18 Zinc Plated Grade 2 Steel Fine Thread Top Lock Nuts

Diameter: 5/8"
Diameter 2: 1-7/32"
Thickness: 35/64"
Material: Steel
Finish: Zinc
Driver Type: 15/16" Wrench
Thread Size: 18 (Fine)
Hardness: Grade 2
Style: Top Lock|Type C
Type: Lock Nut

Box of 5.

A lock nut is a nut that resists loosening under vibrations and torque.