3/8"-16 18-8 Stainless Steel Coarse Thread Keps Lock Nuts (8 pcs.)

Diameter: 3/8"
Diameter 2: 5/8"
Thickness: 13/32"
Material: Stainless Steel
Driver Type: 9/16" Wrench
Thread Size: 16 (Coarse)
Hardness: 18-8
Style: Kep
Type: Lock Nut
Washer Diameter: 21/32"

Box of 8.

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