The way he generates so much power and depth with simple, compact strokes (no big backswings, no extreme wrist action/ windmill, just so solid through the strike zone) he's gotta be using some sort of sledgehammer...that or being 1.9m and 90kg of muscle mass might help.Well we've discussed Andreescu, Medvedev, Schwartzman, Grigor, and Rublev recently... what about Matteo Berretini? What's he using? String and tension? Looks like an older Extreme... which one? Let's go..