I have an m6, and own the 4x6 and the 6x10. I've used the 4x6 extensively. I've compared the 9.5 stock coil to the 4x6 with good results. Went over a couple of areas with the stock coil, and then switched to the 4x6. The 4x6 picked up coins that the 9.5 had missed. Or that I had missed as being a coin. The 4x6 definitely hits the coin targets, and weeds out the trash. I have not owned the 6x10 long enough to tell you about it. I have heard that the 5.3 is also a very good coil.