ShelterPro NCDB430KIT Aluminum Liner and Kit, 30' x 4" Shelter Aluminum liner kits are manufactured for appliances with a.F.U.E. Of 83% or lower UL listed and tested 2 ply Aluminum liner Aluminum mortar collar for slipping the liner through the thimble Aluminum top plate with at 16 inch x 16 inch plate and a 2 inch high collar around the hold diameter Aluminum cap, and installation instructions