Coiltek 14" Mono
The Coiltek 14" Mono has become a proven classic among nugget hunters who use Minelab PI machines. This mono, although somewhat heavy compared to say the stock 11" DD or the 8" mono, has found literally pounds of gold.

This is a deep, sensitive coil which can punch deep. It may be just the ticket for someone who wants to find smaller nuggets at depth or just to punch harder into deep ground for those previously unseen quarter ouncers. Since this machine excels the way it does on both the SD and GP series detectors, it is often the first choice when getting into aftermarket coils.
The 14" mono lists for a retail price of $449 but can be had for around $300. Of course, used Coiltek's can often be found on eBay for much less, perhaps around $100 to $150. Checking around on the nuggethunting forums never hurts either.