This permanent UV marker will write on just about any surface and is ideal for discretely marking any valuable property including hi-fi, TVs, computers and mobile phones. When marked in a concealed area the markings will go unnoticed in daylight. Under UV light though, the ink will light up clearly, identifying all your belongings. The permanent ink is long lasting. For maximum effect and durability, mark your property in a spot that is not frequently touched, like the inside of a battery cover or on the back of a TV or Hi-fi set. Works on most surfaces, including metal, plastic, glass and paper. Ideal for use in combination with the Safescan 40H portable UV detector. Check markings periodically and re-apply if needed.