Heat Fab; HeatFab 304-Alloy 7″ x 24″ Saf-T Liner; 21720 Saf-T Liner come pre-drilled with pop rivets. for insulation, use Heat-Fab Saf-T Wrap – aluminum-jacketed sections of ceramic blanket that snap and lock around your pipe. You can also order 6, 7, and 8 diameter 304-alloy Saf-T Liner in pre-insulated 48 lengths. Features: Material: 304-Alloy. Economical liner for straight chimneys. Seam-welded 24-ga. stainless steel. UL Listed to 1777 Standard with 1 clearance with Saf-T Wrap. 304-alloy has lifetime warranty for woodburning applications. Specifications: Overall Dimensions: 24 (L) x 7 (W).