almost all of the Blue Max series of coils. They include:
Blue Max 350 also referred to as the 4½" Snooper coil.
Blue Max 'Shooter' elliptical 4X6 Double-D, but that was a poor performing coil so forget looking for one of those.
Blue Max 600 which is a 6½" diameter concentric coil, and the replacements for it, the black-colored plastic 5.3 Black Max and 5.3 Bullseye.
Blue Max 800, Pro Scan 800 and Royal 800 8" coils, and a few of the same coil with a different decal, such as the 7.8 that was the stock 8" labeled for the original Quantum II.
The various labeled Blue Max group of 950 coils.
Just remember, the Classic is a 2-filter, slow-motion sweep speed detector, especially if you're in pea gravel, rocks, black sand or other intense mineralized conditions.
Use that Blue Max 600, which is my favorite 6½" coil because I like the white color coil when I am hunting in dense brush as I can view it better.
The coils have to be the Blue Max series of coils and not the older style like they used on the older blue-box 5000D, 6000 D series II, 6000 Di Pro series 3, etc., even though those models also operated at 6.59 kHz, they were not compatible with the Blue Max series of coils that you wouild use on an XLT, 5900 Di Pro SL, Classic ID, etc.
Monte