3M Fast 'n Firm Seam Sealer 08505 is a firm setting product for sealing a variety of external or non-passenger compartment automotive joints and seams. Also used in many non-automotive applications where quick, inexpensive seam sealing is desired. 3M Fast 'n Firm Seam Sealer is a fast setting seam sealer designed for sealing exterior joints and seams. It adheres well to clean primed or painted metal.