I am in the market for a new case of tennis balls and I am looking for some comments on the weight of the Dunlop Grand Prix compared to the balls I typically play with. I have searched and see lots of comments about them being heavier -- but I haven't found anything that compares them to something I play with so I can tell what "heavy" means. My tennis ball of choice is the ProPenn. I think it lasts a good length of time and I like the weight and solid feel of the ball. I also use Tretorns in my ball machine and don't mind the weight of these balls either. However, ProPenns are hard to find where I live and tend to be expensive. So I also will pick up cans of Penn and Wilsons at the local big brand store. I don't particularly like these balls, but these are the most common balls I run across in league play. Since I am ordering balls anyway, I figured I may give the Dunlops a try. So here is my question for anyone who has played with the Dunlops, ProPenns, Tretorns, and others. What is the weight comparison between the Dunlop Grand Prix and a ProPenn, Tretorn Pressureless, Wilson US Open, regular Penn ball? To me, the Tretorn is the heavest of the balls I have used, but I really don't mind playing with them (especially in cold weather). I find them perfect for a ball machine. ProPenns would be next for weight and durability and are my current favorite pressurized ball. However, I have had opponents comment to me that they felt like the balls played a little heavy. Then the Wilson US Open, regular Penns all feel about the same weight wise with the Wilson US Opens seeming to last the longest of this last group of balls. Is the Dunlop GP comparable to the ProPenn ball in weight? Is it heavier and closer to a Tretorn? Lighter and closer to a Wilson US Open? Somewhere in the middle? Thanks any responses!