JacobsParts FLT-D 365nm 5W UV LED Flashlight with Adjustable Focus for Counterfeit Detection, Document Verification, Photography, and Bodily Fluid Identification

If you want maximum effect from "black light" reactive items, 365nm is the best wavelength for this. Ultra-low "visible" light emission shines at a wavelength of 365nm- ensures the stain, not the surface, is illuminated. The 365nm light will appear white on neutral non fluorescent surfaces, where as the 395nm will appear purple. This flashlight produces a near pure UV output which is the optimum frequency for UV fluorescence.

The human eye can perceive light between the range of 400nm and 700nm. 400nm light is perceived as the color violet. The ultraviolet spectrum resides below 400nm. A UV light source that is rated at given frequency will in practice produce light that is concentrated around the specified frequency. In the case of 395nm light, some of the light will bleed into the visible spectrum, thereby producing a violet glow. 365nm is well beyond the the visible spectrum, so it can produce clearer florescence, cleaner more vivid colors, and no violet glow.

395nm is less expensive and can work perfectly well for detecting urine and bodily fluids in the dark, but for document verification, counterfeit detection, photography, and other specialty applications 365nm is a much better choice.