This is a precision 365nm wavelength UV light, necessary when analyzing raw powders and certain products with Substance Test B. This light is included in the Advanced Field Kit, and not necessary for the Individual 2-Step Tests.  

A note about UV lights. High quality lights that emit true 365nm wavelength light can be difficult to find and expensive. We've searched long and hard for a model that would meet the needs of the ROIDTEST system. Whether you choose to purchase a UV light here or elsewhere, we strongly encourage you to avoid "cheapy" lights, as they are often not true 365nm, or the 365nm wavelength may be so nonspecific for 365nm that it will be obscured by too much other visible light.