Replacement cartridge with black control powder 3M Dry Guide Coat Cartridge (09560). The powder is used to identify irregularities in filler or spray putty. The powder is applied in a small amount to the ground surface. After sanding, the powder remains in the indentations or defects, so thanks to the contrasting color, these areas are immediately visible. No masking or drying time is needed. The powder can be used for both wet and dry sanding and contains no solvents.