1/2"-20 Zinc Grade 2 Nylon Thin Lock Nuts LKNUT-119 (5 pcs.)

Diameter: 1/2"
Diameter 2: 27/32"
Thickness: 21/64"
Material: Steel
Finish: Zinc
Driver Type: 3/4" Wrench
Thread Size: 20 (Fine)
Hardness: Grade 2
Style: Thin Pattern Nylon Insert
Type: Lock Nut

Box of 5.

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