Solid-state LED technology offers a low cost and portable source of UV light built into a slim attractive pen. The 400 nm output is just on the edge of the visible light spectrum, low enough to cause fluorescence yet inherently safer than lower UV wavelengths. Includes four LR41 button cell batteries. Replacement #3045-42. Immediate output, no warm up time. Weight: 1 oz. (30 g) with batteries; Size: 3/8” x 5” (10mm x 135mm).