I bought my X-70 used(but like-new), and got the stock coil AND a 6" 18.75 DD coil with it. The former owner told me that I would be amazed at the depth of that little coil. Being from the "old school", I always believed in the old "circumferential convex" theory that a small coil meant shallow, but better target isolation, and a big coil meant deeper targets with poorer target isolation. These theories have been true with the old machines I used to hunt with(and of course they still are, to a certain extent). But DARN!!. That little 6" DD coil is totally AMAZING on depth. How in the hell does it do it??? If any of y'all have thought about getting one for trashy areas, DO it! But you will be shocked at the depth you will get from that little 'toy" coil. I think I'm gonna leave it on my machine.