Is it necessary....no. Is it useful...very. I have a very sloped windshield that makes it difficult to get to the bottom of and clean. This tool works great for that. I use a number of Stoner products and you can't go wrong with them.
This windshield cleaner does the job. It's great for getting into the corners and along all the hard to reach spots on windshields. Especially on those sloped interior windshields most modern cars have. On the inside, it's the way to go. HIGHLY RECOMMENDED