I don't know which coils are available for the Kruzer but I have a CoRe with a Mars Lion coil coming. It will be my first aftermarket coil for the Nokta. That being said, I've tried and own many aftermarket coils for other detectors from Mars (Tiger), Nel/Cors (Tornado, Thunder, Shrew) MGC (5 X
and Detech (10 X 12 butterfly and Ultimate). The two NEL coils were bad unfortunately. The Cors Shrew works well. I really like the Mars and MGC construction quality (beefy coil ears) although I am worried about the wire they use on the MGC which is extremely flexible almost floppy. The Detech is the only one which has very stiff wiring (almost too stiff). They are all light and perform well. Of all those coils, the Detech Ultimate is the one I have used the most. I bought it used and it was battered, bruised, used in water, sand, mud, etc. and still works like the day I got it (and I never used a coil cover on it). Great customer service by Detech as well.