There are three: The 5.75" the 4" and the 7" widescan. For super heavy trash, the 4" is great if you don't mind the small coverage and limited depth. Most prefer the 5.75" which does quite well and works decently as a most used coil as well. The 7" isn't offered as a concentric anymore, but they show up from time to time on Ebay etc. I've used all of them and think you'd probably be best served with the 5.75" although I personally use the 7" concentric for much of my hunting. IMHO you'll find a smaller coil will be much more useful that an extra large coil.
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