The Lennox 17D77 Drain Pan Assembly (21" x 17") is an HVAC replacement component designed to collect and direct condensate produced during the cooling process. Installed beneath the evaporator coil in compatible Lennox air handlers or indoor HVAC units, it captures moisture as warm air passes over the coil and channels the water toward the drain outlet. https://www.partshnc.com/lennox-17d77-drain-pan-assembly-21-x17