TYPE 27 The Best choice for finishing: Used primarily on flat surfaces. The best choice for blending and smooth finishing. TYPE 29 Conical, The Best choice for agrressive stock removal. Conical flap discs have angled flaps and may be used on both contoured and edge work. Why Choose Flap Discs? Flap discs replace both grinding wheels and fiber discs. The same flap disc can be used for applications ranging form stock removal to blending.