Aprea Instruments CalPod solution holder helps users organize all calibration solutions in one place and streamline the entire calibration process. The CalPod can hold up to 4 types of different solutions simultaneously. The hole in the center of the Callbox is for users to place an electrode. After calibration, close the lids so the solutions can be used multiple times. Stickers for commonly used solutions of pH and conductivity are included. Blank stickers are provided for users to label special solutions' names.