I just purchased a new vehicle & my previous vehicle had a wiper on the back window, but this one doesn't. I decided to purchase this to see if it helped with my back window being clearer on rainy days & I am SO happy I purchased this! The rain no longer deters me from seeing clearly out my back window. I purchased this at Walmart for about $4.97 & I think that is a great price for this product! I would definitely repurchase, but I believe this bottle will last for a long while! The bottle recommends you apply it an hour prior to exposing to water & to reapply as needed.