This is a 5 Inch Planar Foot. The main surfaces (planes) are emphasized, so that you can see how everything flows together into groups of surfaces. This is particularly useful for an artists understandings of the forms. But is also helpful for medical students that need to understand A) the primary forms involved, and B) How everything fits together.
The 5 inch version is more sturdy than the 4 inch version, because the tiny toes are larger here. Larger = Less likely to snap off.