Solar Light’s Model 521 Microtops II is a 5 channel hand-held ozonometer for measuring total ozone column per standard WMO configuration easily, accurately and dependably. It measures direct solar ultraviolet radiation at 3 discrete wavelengths within the UVB range, as well as total water vapor and aerosol optical thickness (AOT) using the 936 and 1020 nanometer channels. This meter features 2% accuracy, which is comparable to much larger and more expensive instruments. Highly Accurate Instantaneous Results Portable and Easy To Use Non-Volatile Memory Country of origin: United States Item Weight 1.3 pounds Manufacturer Solar Light Company, Inc Item model number 521 Package Dimensions 15 x 12 x 8 inches