I will second that. Some places I hunt, that hockey-puck sized coil is the only one which can get to the soil and actually get some horizontal movement, places most others avoid. What that coil loses in depth, it makes up with sensitivity, accurate ID and the ability to run the sensitivity wide open in most areas. It responds the least to EMI. Some of my best finds were found with that coil.
Not for the Apex, at least no on-line or from any word from the factory. Ace, Yes. AT, Yes. Apex, No.
John, I really enjoy the performance I get from smaller-size coils in the very dense ferrous debris sites I like to hunt, and I think the 4½" Concentric would be a better performer than the 5" DD NEL coil I'm using now.