Copperfield 69625 6 Inch Dura-Vent Dura/plus Tee Support, Stainless Steel A tee support is used with a side-wall DuraPlus Chimney installation. The construction of the tee support will safely support up to 35' of DuraPlus Chimney. A Tee (sold separately) mounts to the top of the support. The tee support should always be used in conjunction with a DuraPlusWall Thimble. Manufacturer's Limited Lifetime Warranty.