1. UV light used to prevent forgery, authenticate documents, * 2. Spot certain chemical/gas leaks, locate dangerous pests like scorpions or rodents * 3. illuminate proteins, pinpoint leaks * 4. identify protein-based human or pet stains, * 5. Head Diameter 1.375" 38 mm, Body Diameter 1.125" or 27.5 mm Length 3.8" or 94.2 mm, Weight 4 oz.