Though quite firm and durable, Luxilon 4G, choice of Serena & Venus Williams, Alexandr Dolgopolov, Paul-Henri Mathieu, Kei Nishikori and Grigor Dimitrov, to name a few, is loaded with playability. Our testers found this one to have higher than average comfort for a monofilament. Luxilon spent two years tweaking the molecular properties of 4G in order to extend the life of playability. This is a great option for players who want all the benefits of a control string without the high tension loss and impact shock that comes with some of the first generation polys. This doesn't mean it will work for players who prefer natural gut or nylon multifilaments, but it does mean that for players with long, fast strokes Luxilon has created a very user-friendly co-poly.