5/16"-24 Chrome Nylon Insert Lock Nuts LNS-290 (10 pcs.)

Diameter: 5/16"
Diameter 2: 9/16"
Thickness: 23/64"
Material: Steel
Finish: Chrome
Driver Type: 1/2" Wrench
Thread Size: 24 (Fine)
Style: Nylon Insert
Type: Lock Nut

Box of 10.

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