Radial mesh

Antonio Wu, The RZ mesh is meant for axisymmetric models, meaning that at any value of theta the simulation output for a given R and Z coordinate will be the same.  If this is a reasonable assumption in your case, then using a strictly RZ grid is prudent, since it decreases the complexity of your problem from a 3D to a 2D simulation.  If not, then Meshmaker is not a pre-processor you should use to build your grid.  I suggest you look at the TOUGH pre- and post-processors page to find something capable of making a grid like that: https://tough.lbl.gov/software/tough-pre-and-post-processors/