Greer castellated locking nuts come in a wide range of sizes in a hex configuration. The nylon-locking feature is usable in applications up to 250°F. The nylon insert resists most organic acids, oils, greases, and common solvents and mineral acids, as well as abrasive action caused by nicked threads in mating fasteners.The cadmium-plated carbon-steel locknuts come in 0.190 to 1¼-in. diameters. SPS Technologies, 301 Highland Ave., Jenkintown, PA 19046, (215) 572-3305, www.greerstopnut.com