The 3M™ Dry Guide Coat Cartridge is used in the dry primer sanding process to identify surface imperfections such as pinholes and deep scratches in primer. When sanding polyester filler, it ensures the filler is flat with no ripples and that the body styling lines and contours are straight and correct. It also ensures the total primed area is sanded prior to top coating. It requires no masking and there is no dry time involved. It can also be used for both wet and dry sanding and contains no solvents.