It is quite common for reservoir engineers to adjust the geological modelling without recoursing to the geologists by multiplying the porosity, the permeability, the anisotropy (kv/kh), the relative permeabilities, the well factors and many other parameters within their numerical world. Sometimes these factors can be large and global and probably outside the limits of the geological reality. Of course it is not easy to go back and make these adjustments in a close cooperative environment for all sorts of reasons—logistical, technical, management, contractual to name a few. Rarely are these adjustments discussed and certainly there are very few published examples where the loop has been closed. This talk will attempt to illustrate where and how multipliers are applied, what might be the reasons and how the workflows could be streamlined to make closing-the-loop a routine process rather than an occasional occurrence.