The North Face says:
This footprint shields your tent floor from the cool, wet, or abrasive-ground, prolonging the life of the tent floor. Footprints may also be used in fly-only pitching with most models. Cut precisely to fit the Mountain 25 tent.
Current Retail: $60.00
Historic Range: $27.95-$60.00
70D 190T Nylon with 2000 mm PU Coating