Which flap disc should I use?

What type of flap disc is best for grinding metal?

Flap discs are a great abrasive wheel for quick stock removal and provide grinding, blending and finishing with one product. They’re manufactured for use on both mild and stainless steel. Flap wheels made from zirconia (or zirconium) are better suited for use on most metals including stainless steel. Aluminium Oxide flap discs are suitable for most metals, however, excluding use on stainless steel applications.