Fellow tennis nerd and buddy Henrik Wallensten is back. This time with a Slinger bag review, the most popular ball machine in the world? This Slinger Bag review was done during a week where Henrik got to borrow and test the Slinger Bag from FK Sports Nordic. Henrik has now reviewed this product for the Swedish Tennis Magazine as well as Tennisnerd. Word over to Henrik. What is it? I get a lot of questions about ball machines, but I can’t give any straight answers since my experience is limited. The Slinger Bag is a portable ball machine that looks …