Most of use the term string pattern when referring to string density. We call frames with 16 mains "open" and those with 18 mains "dense". In general that's fair description, especially when evaluating the relative string densities of frames with similar head sizes. This quick reference point provides a general context for discussion on frame power, spin potential, and control as they relate to string density. BUT...I'm now certain this quick reference point can be very misleading if accepted whole cloth. 16 mains means an open, spin friendly, powerful frame, right? 18 mains means a dense, control friendly, lower power frame, right? I had been a huge fan of frames with 16 mains in a never ending search for spin-controllable power. I started out near the upper end of the spectrum of 100" frames with 16 mains working my way down to the 90" AG 100 and 93" PB10 Mid. After trying all sorts of 16 main frames I then tried the PSLGT with 18 mains. Low power but very spin friendly and control oriented, even at 95". Curious about how far I could push this "dense pattern in a large frame" I tried several 100"+ frames with 18 mains settling on the Head Speed MP 18x20. Now here's the interesting part... The 100" Speed MP 18x20 has the same string density as the 16 main 93" PB10 Mid as measured across the 12 center mains. I enjoy both frames for the level of control they offer. They feel pretty darn precise. The PB10 Mid is certainly spin friendly but the MP18x20 definitely has the edge in that department. the PB10 Mid feels more powerful to me. The result is that I enjoy both frames with the PB10 Mid generating deeper, lower, faster shots and the MP 18x20 generating spinnier, safer, but somewhat slower shots for the same stroke. After examining the "12 Center String Density" of other frames I've used I realized that my preferred limit is about that of the "open" PB10 Mid and "dense" MP 18x20. In other words it's not really number of mains but the space occupied by the 12 center mains. As I go past that density into more open spacing I have progressively greater difficulty controlling the ball. As I move below that point I have an easier time controlling the ball (eg PSLGT and AG 100). And along that spectrum spin potential rises or falls and becomes more or less important with head size and power. It all makes me wonder if there isn't a better measure for string density than total number of mains. Maybe some value such as the ratio of space occupied by the 12 center mains which dominate the sweet spot. As far as I can tell it's that value plus head size and stiffness that best describes how a frame plays...16 vs 18 seems less important in light of the fact that frames with 16 mains can be as precise as those with 18 while some 18 main frames can generate more spin than their 16 main counterparts.