Rainax can be found at many local stores, I am using this for my car windows. I cannot see properly if there is rain and using wiper is not going to help. With this I can see better and drive safely!
This is good for you and your car because you can drive safe home. If there is heavy rain you don't need to worry that you don't see well. If it is very heavy rain then it is hard to say.
It is just my review as product is purchase by me!