This Alu Oxyd Mini, also known as the Aluminum Oxide stone, has a grit of 180 (fine). This makes it ideal for removing rust and burrs, for example, before you start sharpening. This way your file will stay sharp for longer.
In addition, this Alu Oxyd Mini is also very useful for repairing your ski or snowboard. When you are going to repair it with a P-tex drip candle or with a template and epoxy, the Alu Oxid Mini makes it easier to finish the repaired base flat.