3/8"-16 Black Phosphate Grade 2 Steel Coarse Thread Lock Nuts

Diameter: 3/8"
Diameter 2: 21/32"
Thickness: 21/64"
Material: Steel
Finish: Black Phosphate
Driver Type: 9/16" Wrench
Thread Size: 16 (Coarse)
Hardness: Grade 2
Style: Top Lock|Type C
Type: Lock Nut

Box of 352.

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