This file folder game helps students practice estimating mass as about a gram, over a gram, about a kilogram, or over a kilogram. Six examples are provided for each category showing real-life examples of the mass of common objects. This file includes a front label for a file folder, a file tab label, answer key, two page sorting mat, and 24 pictures of items to sort into the four categories. This activity supports third grade Common Core measurement standards. Hop to it!