This is a really good quality source of real UV light (not just a purple bulb), that is compact enough to sit amongst your bunch of keys, and reliable enough to use in counterfeit money detection, many UV torches have enough UV to make neon cosmetics glow in the dark but few have the ability for real detection purposes such as picking up Smartwater or the marks on passports, driving licences, and credit cards. Non replaceable batteries included5cm diameter x 1cm depthUV Counterfeit Keyring Torch