Fisheye lens is a super wide angle lens.
Such as 180°, 185°, 190°, 200°, 210°, up to 240°.
Mostly are M12 lenses.

Towin Lens has many fisheye M12 lenses, for example CCL23020MPF.
It is a max image circle Φ6.4mm and 210° as picture showed below:

Fisheye lens, M12 lens, super wide angle 210°

Fisheye lens, M12 lens, image circle Φ6.4mm