Right off the 300 Below web site.
Materials Impacted
Steel, Iron, Copper, Aluminum, Carbide, and some Polymers are all able to benefit from our cryogenic tempering process. If we add an optional heat treatment after our freezing process, we have termed this “cryogenic tempering” because of the additional benefit. Since all changes to metals take place on the quench, our cryogenic treatment process is a natural extension of the heat treatment process that your parts are normally subjected to.
And...
Reduce Metal Stress and Fatigue
We freeze at-risk metals to -300°F, causing structural changes at the molecular level to make your wearable parts more resilient. This helps fight corrosion, breakage, and wear – reducing unnecessary stress on your metal parts.
So like I said, they can do a heat treat option.
And it changes molecular structure.