Serrated hex flange nut, flange lock nut (serrated), toothed flange nut, washer-faced nut, integral washer nut, anti-vibration flange nut, M5 serrated nut, M5 flange fastener. The integral flange spreads the load like a built-in washer, while the serrations bite into the mating surface to help resist loosening from vibration.
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