Sensitivity
Models M-55, M-65, M-96, M-100, FX-3 and TW-6

Predicting the depth-penetration power of a metal detector is a difficult task. That's because heavily mineralized soil can reduce a metal detector's depth-penetration power. And chemicals in the soil can corrode a metallic object, actually increasing a detector's depth-penetration power. Also the shape of an object and how it lies in the ground has an effect on depth-penetration power. A ring, loop, or dish-shaped object lying flat produces the best results, whereas a rod-shaped item, especially when scanned end-on, is very difficult to detect (except with the FX-3, which only responds to iron or a magnetic field.) Here are some approximate penetration depths of Fisher metal detectors.