The Streamlight LOGO keychain light weighs less than half an ounce with batteries. The amount of features it has is unbelievable! It has three light levels, plus a blink mode (which will flash for 45 hours). With battery conservation in mind, when the light is in High, Medium or Low modes, it automatically turns itself off after 6 minutes; but it flashes a warning first, so you can keep it turned on if you want. Not bad for a 10 Lumen keychain light.