Helix Racing Exhaust Screen 12 X 18 in Stainless Steel Stainless steel exhaust screen is used to enclose muffler packing to prevent the packing from blowing out and provides more uniform exhaust flow .011 diameter stainless steel strands are interlaced together to form a two layer sheet that is crimped on two sides for easy insertion of muffler packing material Sheets are cut to 12in. x 18in. to fit most mufflers/silencers