Meike designed a very good quality circular fisheye for APS-C size sensors, it is renowned by VR photographers and videographers for its good optical quality and good value for the money.
It features a small slip-on front cap.
It does heavy despite the small size, it has a good feeling and good construction but bad quality check.
Be prepared to test extensively the focus and to give it back if not satisfied.
It may not go completely in focus at infinite, or go beyond that.
A 100% working example is worth the risk and if you are good at bricolage you can fix the focus issue by yourself following the video on the link below:
Focus ring misalignement fix
The lens sports around 190° of FoV, even some degree more, in fact. It’s also sold with Opteka and Altura names, same look, nominal values, colors, and optical scheme.