I have the factory 9 inch and the 6in hf dd coil. I go to a local old park here and its just blanketed with pull tabs and tinfoil. The 9 inch has multiple hits on every sweep and is impossible to isolate good targets from bad. I have tried the 6 in hf also there also and the dd does do a better job of seperating targets but I think the hf is just to much for targets there. I am beginning to think I need a 6 inch med freq dd for trashy parks and a 10.5 in med frequency for wide open spaces like at the beach. Seems to be alot of rave reviews over the 10.5 dd med freq coil . any opinions would be appreciated .