Durable black colored aluminum oxide in medium grits.
Primarily used for block hand sanding, 3M WetorDry sandpaper has a more aggressive cut than production paper of the same grade.

The ability to use it with water provides several advantages:
Water acts as a lubricant, allowing for better cutting with less effort.
The use of water also makes the sanding process dustless and helps keep the abrasive surface cleaners.

For fine sanding prior to compounding
Ability to use wet keeps dust down
"A" weight paper backing