# FLEX Saline Sensor Kit
The FLEX saline kit includes 34 saline sensors. Each sensor is silver/silver chloride plated and has three prongs to grip the sensor felts—the same as EPOC X.
### Hydrating the Sensor Felts
To hydrate the sensor felts:
1. Place them in a glass;
2. Cover the felts in saline solution and soak.
3. When the sensor felts are thoroughly soaked, remove them from the glass and squeeze out the excess fluid.
4. They are now ready to be inserted into the sensors.
### Rehydrating the Sensors During an Experiment
Saline sensors will start to dry out during an experiment. The time they take to dry out will depend on the environment you’re working in. The contact quality map in PRO will show any changes to the contact quality during your experiment. For example, the contact quality will change from green to orange as the felts dry out.
You can top up saline at individual sensors without interrupting your experiment. To top up the sensor felts, add a few drops of saline to each felt through the opening at the top of each sensor. After a few seconds, you will see the contact quality at each sensor improve.
**TIP:** If you want to slow evaporation, we recommend adding a few drops of glycerine to your saline solution.
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