3 inch - Mini Zirconia Flap Discs, the Rol-loc discs for grinding.  Use them on welds, rust, or whatever you need to grind and finish in one step.  These discs are layered making them last 10 times longer than a regular sanding disc. The fresh abrasive is continuously exposed so they won't glaze over.  Sold in packs of 10. **BUY  2 PACKS OR MORE AND GET A FREE 3" MANDREL BACKING PAD WITH ORDER.