Wall sleeves and penetration covers are used for a through-wall penetration. The wall sleeve creates a neat hole through the wall, and the line set is covered by the wall cover. The sleeve is designed to allow for easy installation - even after the line set has been installed. A unique hooking and fastening arrangement allows for quick and easy installation. Each wall cover is furnished with stainless steel screws to attach the wall cover to the base. Three screws (supplied by others) are needed to fasten the wall cover to whatever type of wall construction the system is being installed on.