It is easy to lose perspective on the scale of features while working in CAD. When designing cell-phones, where .25 mm can be significant, having some real-world reference for how tangible a feature will be is critical. We created the attached geometry and machined a copy for each designer so they can evaluate features in real-time while building CAD models. The part contains positive and negative features from .25mm to 1.25mm and parting lines at each dimension. The four corners of the block are rounded at .5,1,1.5, and 2mm.
You can download the IGES file here: radii_reference