For tubes 1/ 4" -3" ( 6.4-76.2mm) I.D. Flex-Hone Abrasive Tools are light pressure, soft application honing devices for cleaning straight, ferrous tubes. They consist of 180 grit silicon carbide abrasive globules ( stones) bonded to high density nylon filaments. Order tool to correspond to tube I.D. Note: Flex-Hone Abrasive Tools are normally used with a water flush for maximum life.