Define 'one' yes I know it sounds odd. The LEDs come on stars, said star can have anywhere from 1 - 4 (sometimes more) bulbs on it. Yes one will work but finding a good one that can be seen well is an issue I'm having in part due to lack of experience and lack of money to throw at the problem. I currently run a single cree XP-E in white turned to red and it's barely visible in indoor lighting. I hear the XP-E2's are supposed to be pretty good, I'm also debating about just getting a really beefy white and doing something so it will be red.