5/8"-11 Black Phosphate Grade 2 Nylon Insert Lock Nuts (58 pcs.)

Diameter: 5/8"
Diameter 2: 1-7/32"
Thickness: 49/64"
Material: Steel
Finish: Black Phosphate
Driver Type: 15/16" Wrench
Thread Size: 11 (Coarse)
Hardness: Grade 2
Style: Nylon Insert
Type: Lock Nut

Box of 58.

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