The most significant quantity in all these criticality experiments is the mass of the assembled fissile material in the benchmark assembly when it is close to the criticality point (critical mass). Measured physical parameters (other than nuclear data) that influence determination of the critical mass are the geometry of the fissile material, its isotopic composition and density, the geometry and material composition of the support structure, and characteristics of the surrounding environment. The neutron leakage from cylinders with various geometries is rather sensitive to the energy-angular distribution of neutrons scattered in the benchmark fissile material and less sensitive for geometrically similar spheres. Uncertainties of the physical parameters (e.g., dimensions) for manufactured cylinders of fissile material are much smaller than those for comparable spheres. Criticality measurements are very sensitive to fissile material geometries. Errors in determining benchmark physical parameters, underestimation of their uncertainties, failure to apply required corrections, and deficiencies or simplifications in the models used in simulations can affect the ∆k eff comparisons significantly. The excessive impact of these benchmarks on **data** validation and/or **data** adjustment could be mitigated by considering USU.