The 74064 Cornerstone 260 Triple Ruled Grating Assembly is mounted in an individual, prealigned mount. Simply drop it in place, and program the grating specifications into the Cornerstone 260 through the Control/Utility Program or Hand Controller. This grating assembly has a 1200 l/mm line density and has a peak efficiency of 80% at the 750 nm Blaze Wavelength. It's efficincy exceeds 20% over the 200 to 1400 nm primary wavelength region. 1400 nm is the Cornerstone 260's upper wavelength mechanical limit for this grating assembly. You can add and change gratings in the field without changing the instrument’s grating turret. However, you may have to replace your current grating assemblies. If you wish to convert your Cornerstone 260 from this triple grating to a dual grating (to improve resolution), you will need to purchase the equivalent 74164 Dual Grating Assembly.