400 grit sheets are best for wet sanding before coats of primer Made with a premium grain, which offers a higher cut rate and uniform scratch pattern which makes it perfect for achieving fine finishes When sanding wood, 400 grit waterproof sheets are ideal for final smoothing to top coats Use dry during the preparation phase of a project, usually when removing existing finishes, rust and oxidation; it is also key when sanding and shaping body fillers and primer coats Sheets can be cut-to-fit 1/2 sheet, 1/3 sheet, or ¼ sheet sanders