We are dealing with measuring instruments 1.Use as level and slope meter 2.Aluminum frame 3.Magnetic Bottom 4.The display flips over when the bottom faces up and automatically off in 15 minutes after use 5.The Sea level is permanently set inside the chip, zero setting is not needed when battery is replaced 6.Buttons: On/Off , Zero, absolute and incremental measurement 7. One AAA battery, automatic power off in 5 minutes