...
This is the mesh's quality level: the better the quality, the more polygons, and the longer the mesh creation time. Choose from five levels. And here is how the polygon size is calculated based on the "Radius" parameter:
...
Radius
To create the mesh, RealFlow | Cinema 4D creates spheres around the particles and blends them. The size of these spheres is controlled here:
...
A value of 4 or 5 is sufficient in most cases. Higher values (6-7) can be used to close small holes in the fluid or remove unwanted patterns. With settings of 8 and more, many details will be lost.
...