The way that ad is worded is kind of misleading even though what's written is accurate. That's a standard BH four inch coil and it does have a narrow search field compared to larger coils, but only because of it's size. It is more sensitive to small objects, but that's also because of it's size. A detector transmits the same amount of energy regardless of what size coil is used, the smaller the coil the more intense the transmitted field, and the result is that small targets are more easily detected. Small coils work better in bad ground for the same reason. They see less ground than larger coils, which means they also see less mineralization. The ad doesn't mention gold nuggets, most likely because that coil is for the lower frequency BH models and frequencies of 15 khz and higher are used on detectors designed to hunt nuggets.
