Ceramic Pro Rain is a Super Hydrophobic Glass Coating

Permanent Protection Scratch Resistance (Above 9H) Super Hydrophobic Effect Weather & UV Resistance Thermal Resistance (up to 750°C) Anti-Graffiti Advanced Chemical Resistance Oxidation & Corrosion Resistant High Gloss Finish

Ceramic Pro Rain is a coating specifically designed for glass with excellect durability without affecting the motion of the front wiper blades, the super hydrophobic effect of the coating means water will simply bead up and run off the glass whilst you are driving. 
Unprotected glass can be a hazard in the rain as water can stick and sheet over the windows decreasing visibility and become a safety hazard, by having Ceramic Pro Rain on all windows this will increase visibility by repelling water and allowing it to bead up and roll straight off the glass, this will also keep the glass cleaner for longer as dirt and grime will no longer stick.