The Tilt hydrometer allows you to check the specific gravity and temperature of your beer while it's fermenting, without ever having to open your fermenter or pour out any of your precious brew. This makes brewing more consistent and easy to track. Each Tilt comes calibrated and ready to go with a pre-installed battery that lasts 12-24 months depending on usage. Just download the free app, drop in your fermenter, and start taking readings with your phone, tablet, or Tilt Pi. The specific gravity is accurate +/- 0.002 within the Tilt's range of 0.990 to 1.120. The thermometer is accurate +/- 1 degree F (+/- 0.5 degree C). If using multiple Tilt hydrometers for different batches of fermenting beer you must use a different color for each batch. The app will not read multiple hydrometers of the same color. Download the free Tilt app at the Apple App Store or Google Play Store or get the free Tilt Pi download.