This five pack of Holographic Diffraction Gratings 500 lines/mm are highly-efficient, embossed Holographic Optical Elements (H.O.E.), and ideal for the direct viewing and analysis of spectra from gas tubes and other light sources. The quality of the spectrum produced is the brightest possible with a minimum of distracting visual noise. Try using these diffraction gratings in conjunction with colored film gels for additive and subtractive color demonstrations! Dimensions: 2” X 2”.