Flap Disc The flap disc is made from aluminum-oxide with a high stock removal rate and is ideal for grinding and smoothing of cast iron, gray cast iron, stainless steel, steel, non-ferrous metal, wood and plastic, NO 28 591 150 grit Proxxon 38544 Longneck Angle Grinder LW/E, Proxxon 38547 Long Neck Angle Grinder LWS, SKU: PXTECH190