Whirlpool thru-the-wall sleeves are required for a first time installation. If you are replacing an existing thru-the-wall unit you may be able to use the existing sleeve with our model. Whirlpool thru-the-wall sleeves are manufactured with a multi-baked enamel finish for maximum corrosion resistance. Sleeves come with front and back covers with center supports for secure installation into any wall. Also included is a front gasket to help eliminate drafts and seepage from the elements as well as a rear grille.