Nimonic alloys typically consist of more than 50% nickel and 20% chromium with additives such as titanium and aluminium. The main use is in gas turbine components and extremely high performance reciprocating internal combustion engines. Due to its ability to withstand very high temperatures, Nimonic is ideal for use in aircraft parts and gas turbine components such as turbine blades and exhaust nozzles on jet engines, for instance, where the pressure and heat are extreme. It is available in different grades, including Nimonic 75, Nimonic 80A, and Nimonic 90.

Nimonic exhaust valve spindles are well accepted now that operators have become acquainted with the long-lasting seat performance, despite dent marks. Nimonic spindles are standard for 50MC and 60MC/MC-C engine models upwards; and Stellite spindles are standard for smaller models.