According to an original Elastic Stop Nut Corporation of America (ESNA) Catalog. . .

• "Under normal operating conditions, the red fiber insert provides completely

  satisfactory and economical locking effectiveness, retaining its locking torque for a

  minimum of 15 installations and removals."

• They were also made with red nylon inserts, which were good for fifty installations

  and removals.

Another advantage in using types with Fiber or Nylon Locking Inserts is that you can reuse them

over and over again without damaging the screw or bolt threads.