Prime-Line #4-40 Grade 2 Zinc Plated Steel Nylon Insert Lock Nuts 50-Pack)

Lock nuts (or locknuts) feature a nylon insert that grips onto threads and resists loosening due to vibration. It is best to only use each nut once as its holding power is reduced if reused. They should not be used in extremely high heat or in certain chemical environments as that could weaken the plastic insert.

• Installs easily with most wrenches
• Designed to be used with the same sized screw
• Steel construction offers long-lasting use and solid performance