It is most commonly labelled Nitronic 50 (AK Steel Group) or Fermonic 50 (Langley Alloys), which usually refers to grade XM-19 according to the American ASTM specification, the European Iron and Steel Standards Institute (EISI) 1.3964 grade, or the UNS system S20910 grade.

It is an austenitic stainless steel similar to the more standard grades in the same family such as 304 L and 316 L. It is as easy to forge and weld as it is non-magnetic, plus it maintains its mechanical properties over a wider temperature range. However, XM-19 offers improved corrosion resistance and strength.

The improved corrosion resistance of XM-19 is achieved through a significant increase in chromium and nitrogen content, which improves the formation of stainless steel passivation films.

Looking first at Pitting Corrosion Equivalent (PREN), PREN is a useful theoretical approach to comparing the pitting resistance of various types of metals based on their chemical composition.

PREN values can be used to compare different grades of material, but cannot be used to predict the absolute performance of a grade in a particular application. The most widely accepted content of the PREN formula calculates the equivalence of chromium, molybdenum and nitrogen. PREN = % Cr + 3.3 x %Mo + 16 x % N. For 316 L the PREN value is 25, for XM-19 34.

316 L has a PREN value of 25, XM-19 has a value of 34, similar to duplex stainless steel ("2205").

The addition of nitrogen also contributes to the strength of the alloy. Under standard annealed conditions, XM-19 has a yield strength of 2 times that of 316L; however, under hot rolled conditions, XM-19 has a yield strength of 4 times that of 316L. Not only is it strong, but it is also very tough.

When describing metal materials, toughness is usually measured in terms of impact strength. This test records the amount of energy absorbed per unit of cross-sectional area when a specimen breaks or fractures under an impact load. The higher the number, then the metal can resist a greater impact load. For XM-19, this impact strength can be maintained at temperatures as low as -196ºC. This is critical for valve stems, as valves can be inactive for long periods of time, and if the valve is sticking, then a greater force is required to open or close the valve. Therefore, the strength and toughness of XM-19 over a wide range of temperatures is the basis for its consistently excellent performance.