1/2"-13 18-8 Stainless Steel Coarse Thread Serrated Lock Nuts (6 pcs.)

Diameter: 1/2"
Diameter 2: 27/32"
Thickness: 15/32"
Material: Stainless Steel
Driver Type: 3/4" Wrench
Thread Size: 13 (Coarse)
Hardness: 18-8
Style: Serrated
Type: Lock Nut
Diameter 3: 1"

Box of 6.

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