Smooth out irregularities in concrete and hardwood floors with this Screen-Bak Durite Q421 SC coarse grit screen floor sanding disc. Its P-graded sharp silicon carbide grit easily cuts into even the hardest floor surfaces and its open-weave screen design provides extreme resistance to loading during lighter jobs, such as cleaning off scale and rust. This durable sanding disc, which exhibits greater durability than paper or cloth, is waterproof, so you can rinse it off between uses and extend its service life.