For AAR (American Association of Railroads) applications.
This model, when properly installed, meets or exceeds the performance requirements of the America Association of Railroads (AAR) standard M-931, Truck and Trailer Manufacturers Association (TTMA), and the Society of Automotive Engineers (SAE).
Specifications:
Material: AISI 4320H and 4718H
Hardness: 380-420 BHN
Quality: Manufactured to a proprietery standard for both
surface and interior sound, and for dimensional
accuracy.