Nylon inset lock nuts nuts are basically a hex nut with a nylon-filled collar at its back end. When a screw reaches the collar, the threads and nylon form a tight, frictional fit, restricting movement of the screw when it's subject to vibration.
Unit of Measure
Items
GRADE C NYLON INSERT LOCKNUT, NE, ZINC YELLOW CR+6 (INCH)

1/4-20 NYLON INSERT LOCK NUT NE SERIES GRADE 8 YELLOW ZINC
Web Price $185.33

GRADE C NYLON INSERT LOCKNUT, NE, ZINC YELLOW CR+6 (INCH)

1/4-28 NYLON INSERT LOCK NUT NE SERIES GRADE 8 YELLOW ZINC
Web Price $213.62

GRADE C NYLON INSERT LOCKNUT, NE, ZINC YELLOW CR+6 (INCH)

1/4-20 NYLON INSERT LOCK NUT NE SERIES GRADE 8 YELLOW ZINC
Web Price $10.47

GRADE C NYLON INSERT LOCKNUT, NE, ZINC YELLOW CR+6 (INCH)

1/4-28 NYLON INSERT LOCK NUT NE SERIES GRADE 8 YELLOW ZINC
Web Price $13.05

GRADE C NYLON INSERT LOCKNUT, NE, ZINC YELLOW CR+6 (INCH)

5/16-18 NYLON INSERT LOCK NUT NE SERIES GRADE 8 YELLOW ZINC
Web Price $205.77
Diameter N/A 1/4 N/A 1/4 N/A 1/4 N/A 1/4 N/A 5/16
Pitch N/A Coarse N/A Fine N/A Coarse N/A Fine N/A Coarse
Length N/A
Material N/A Grade 8
Finish N/A Yellow Zinc Plated
Package Quantity N/A 3500 N/A 3500 N/A 100 N/A 100 N/A 3000