MSR lumber is evaluated by mechanical stress-rating equipment to measure modulus of elasticity (E), but it also must meet certain visual grade requirements. Unlike visual lumber grades, the evaluated properties become the grade identifier, and are placed on the stamp. 

MSR lumber is intended for any engineered application where low variability in strength and stiffness properties is primary product consideration, e.g. trusses, floor or ceiling joists or rafters. Grades are designated by Fb and E. The grade stamp may also include allowable stress parallel-to-grain (Ft), and specific gravity (SG), for horizontal shear (Fv) and compression perpendicular-to-grain (Fc | ) values, when any of these additional properties are specifically qualified through testing and daily quality control. Grades are: 

  900 Fb-1.0E
1200 Fb-1.2E
1350 Fb-1.3E
1450 Fb-1.3E
1500 Fb-1.4E
1650 Fb-1.5E
1800 Fb-1.6E

1950 Fb-1.7E
2100 Fb-1.8E
2250 Fb-1.9E
2400 Fb-2.0E 
2550 Fb-2.1E
2700 Fb-2.2E
2850 Fb-2.3E