Each part is media-blasted to remove all paint and rust. Ideally, choose parts void of dents and imperfections. When you media-blast, be gentle with the blasting. Hard sandblasting will warp and distort the steel. Media-blast just enough to remove rust and paint. Believe it or not, you can media-blast so hard you peen the metal, making valve covers and air cleaner so warped they won't fit.