Hillman Stop Nut 1/4-20 is designed for secure fastening applications where preventing loosening from vibration is critical. These nylon insert stop nuts, commonly known as stop nuts, fasten onto bolts to mechanically join materials together with reliability. The unique feature of this stop nut is the nylon insert located at the top of the nut, which grips the bolt threads tightly to prevent backing off or loosening over time. This ensures a strong, durable connection in various construction or repair projects. Model Number: 1/4-20