Question about AT Pro 8.5 x 11 coil

I use the 8.5 by 11 in fields, but prefer the smaller coil in yards and parks.

My 5by8 never comes off unless I might use the 11 inch at a beach.

Sounds like I'm different than the other responses as I only have the stock 8.5 by 11 coil so use it exclusively. I hunt curb strips and private yards, and have had excellent results with my AT Pro with the stock coil. To a degree, I think it depends on where you are detecting and how deep the coins are. The larger coil, from what I understand, will give you perhaps and inch or two more depth, but may suffer performance in really trashy areas. The coins are not super deep where I live, so here probably either coil would be able to locate them, and the yards and strips are not too trashy so my larger coil does fine. When I detect a yard that has a lot of grass or extra topsoil, I am glad to have that larger coil on my machine.

My 8.5x11 is down with a bad wire and I miss it. I'm switching between my 5x8 and Nel Attack but the Attack needs a lot of clear space and I lose depth with the 5x8. The 8.5 is a nice balance.

Both my AT Pro and my Ace 400 have the stock 8X11 coils and I do very well with them. I see no need to spend money on another coil. Also, many guys claim that the stock coil is too nose heavy but I don't find that to be true at all.