I have to say that I am very impressed with the 6" dd coil. Hunted a yard that was loaded with brass and copper plumbing parts, car parts, pieces of aluminum antenna, and you name it, it was in there. Had the 70 in 4 tone, sensitivity at 28, no discrimination. The machine was very stable. The plumbing parts would fool me once in awhile if they were small. Found some older clad, an old pendant off of a necklace, and 1906 IH at about 6" deep. I have hunted this yard with the standard coil on the 70 and also with the F-75, which is 4sale by the way. The 70 with the 6"dd is a great combo. if you hunt in these type of conditions.