Yesterday each student used the balance scales, putting a 5 gram mass on one side. Then all combed the classroom to find different items that would balance the scale. A baby vole weighs about the same as one unifix cube OR one nickel OR one tiny plastic zebra OR one small rectangular lego OR one die OR one small bristle block OR one tiny bivalve shell OR one medium plastic bear !
Since there are usually about 5 baby voles in a litter (each weighing 4-5 grams), you could mail a whole litter of voles in an envelope with one 44 cent stamp… and probably fit in a short note as well! [NOTE: one ounce = 28+ grams]