This slim design keyring is manufactured with a super bright COB LED & handy carabiner hook. It requires 2 x CR2032 button batteries which are supplied. Chip on Board (COB) is the most recent development in LED technology using chips with multiple diodes (typically 9, or more). There is no casing with COB technology which enables a much denser array of light compared to SMD or normal LED bulbs. It is ideal for camping, vehicle, emergency, household use etc.