Cell-level neutronics often involves absorber cells. Cell details are homogenized and the cylindrical cell is presented in box form to a higher level of calculation. Neglect of either the non-reflective nature of the cell boundary or its rectangulation will produce errors. Such errors may be avoided by including in the input to the higher-level calculation, namely the homogenized cross sections, flux ratios. One forms a ratio of the flux produced in the calculation of a detailed, cylindrical, cell to the flux produced in the calculation of the box-like, homogenized, counterpart cell. In the higher-level calculation these ratios are to multiply absorption and fission rates.