Fully waterproof, the tiny Impulse from Princeton Tec features an electronic switching system with five settings for its L.E.D. bulb-low, medium and high burn, and fast and slow strobe. The Impulse has a quick release, detachable clip and hat clip option, so you'll want one for every keychain, backpack, ball cap & book bag. Includes 2 lithium coin cell batteries. Available in 4 colors, all with a white LED.