3/8"-24 18-8 Stainless Steel Fine Thread Serrated Lock Nuts (5 pcs.)

Diameter: 3/8"
Diameter 2: 5/8"
Thickness: 11/32"
Material: Stainless Steel
Driver Type: 9/16" Wrench
Thread Size: 24 (Fine)
Hardness: 18-8
Style: Serrated
Type: Lock Nut
Washer Diameter: 3/4"

Box of 5.

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