The BAUER™ 4-1/2 in. x 5/8 in.-11 40-Grit Type 27 Flap Disc is constructed with high quality Zirconia Alumina grain that lasts up to 2X longer* for fewer disc changes. Flexible flap plates conform to surfaces for grinding and blending on curves and contours. This disc delivers high performance on carbon steel and stainless steel applications.