The service life of the built-in battery is about 5 months depending on the frequency of use. The battery can be replaced with a one when it is exhausted. Battery model: LR03 alkaline zinc manganese battery PH/EC/TDS/ORP/TEMP/residual chlorine six-in-one Bluetooth water quality pen Note:Make that the sealing ring (its own) is tightened and put into the water. No sealing ring or untightening will lead to water ingress. Type:B:With calibration powder Colour:As Shown Material:ABS Size:160x26x90mm Package Contents: 1 * Water quality detector 5 * calibration powder Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.