These pressure classes also have differing pressure and temperature ratings for different materials. Unique pressure classes for piping can also be developed for a process plant or power generating station; these may be specific to the corporation, engineering procurement and construction (EPC) contractor, or the process plant owner. The ASME pressure classes for Flat-Face flanges are Class 125 and Class 250. The classes for Ring-Joint, Tongue & Groove, and Raised-Face flanges are Class 150, Class 300, (Class 400 - unusual), Class 600, Class 900, Class 1500, and Class 2500.