This is Dremel's Aluminum Oxide 5/8" Grinding Stone Accessory Bit.
A high-quality industrial abrasive made for extended usage.
Use on metals, castings, welded joints, rivets and rust.
Ideal for sharpening, deburring, cleaning and general purpose grinding of most materials--including stainless steel.
Specially designed for working with flat and slotted surfaces.
Remove rust from cars and bicycles.
Sharpen fishing lures.