Abrasion resistance of a material is reported as loss of:

Abrasion resistance testing of refractories, especially under ASTM C704 as referenced by API 936, evaluates material durability by measuring theloss of volumeafter a defined wear process using silicon carbide grit. This test simulates erosion environments (e.g., FCCU risers) and outputs the result incm³ or in³ of volume loss.

Loss of mass or density may also occur, but volume is the defined reporting metric.