5/16"-24 Zinc Plated Grade 2 Steel Fine Thread Top Lock Nuts

Diameter: 5/16"
Diameter 2: 9/16"
Thickness: 17/64"
Material: Steel
Finish: Zinc
Driver Type: 1/2" Wrench
Thread Size: 24 (Fine)
Hardness: Grade 2
Style: Top Lock|Type C
Type: Lock Nut

Box of 16.

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