This small, pocket-sized gadget really comes in handy for anyone with low vision. Just place it on the rim of a mug, pour in the hot coffee, and wait for the tone to sound. This durable, orange-colored item means you don't have to tell when to stop filling the cup by hooking your finger over the rim ... and thus burning your fingertip. It's also a great item to have when you're entertaining guests; it eliminates the embarrassment of overfilling cups of coffee, tea or juice. Whether you're measuring hot water, pouring a cup of milk, or filling a glass with juice or pop, our Liquid Level Indicator makes the task easy and sanitary. Simply hook the device over the rim of a cup or pot. The prongs will hold the device in place, and the indicator is so light it won't tip even small cups over. Pour until the unit beeps (telling you the liquid is getting close to the top). Fill carefully until the tone changes (warning you the liquid is within an inch of the top), then stop pouring and serve. That's it! Takes two AAA batteries, not included.