Read my 12x10 thread. So far it looks like it's deeper than the stock 10" Tornado in my highly mineralized ground, where as the 15x12 got less depth than the stock 10" coil but did go deeper in the sand. The 12x10 seperations in the left/right perspective better than the stock coil IMO. It's detection field feels razor sharp. The sounds are more responsive/crisper/etc too. The coil seems to run stable at higher sensitivity settings than the stock coil and doesn't false as much either. In my limited head to head testing so far the 12x10 appears deeper. For instance, at a 3PM sensitivity setting in high minerals the stock 10" coil didn't even response to a silver dime 7.5" deep, while the 12x10 hit it fine. The 12x10 also appears to hit max fringe depth coins with a good ID while the stock coil has major trouble with it. Don't get me wrong, the stock 10" Tornado is a great coil. Much better than the 10" Explorer coils IMO, but the SEF is a further step up in seperation, pinpointing, stability, etc. It feels like the clock speed of the machine has been sped up due to the sharper/more reactive detection field too. I like it so far. Just that I've only dug one real deep silver with it thus far (perhaps 7.5 to 8.5" deep, can't remember), but I have dug wheats at 8.5" or so in dry soil with it, so that's saying something. To be fair I haven't done much hunting at known deep coin spots with it yet.