#4-40 18-8 Stainless Steel Coarse Thread Keps Lock Nuts (30 pcs.)

Diameter: #4
Diameter 2: 9/32"
Thickness: 1/8"
Material: Stainless Steel
Driver Type: 1/4" Wrench
Thread Size: 40 (Coarse)
Hardness: 18-8
Style: Kep
Type: Lock Nut
Washer Diameter: 9/32"

Box of 30.

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