Today, SPS Technologies’ FLEXLOC self-locking nuts are used by the military and aerospace industries in airframe, space vehicle and missile assemblies; piston, turbine and rocket engines; as well as ground support equipment. Virtually every major military and commercial program in production today utilizes SPS self-locking nuts.
https://www.pccfasteners.com/assets/local/documents/product-literature/flexloc_cat_sp1040.pdf

