A container refrigeration unit (10) is provided. The container refrigeration unit includes a container (20), a curtain (30), a seal element (40) and a sealing adapter (50). The container includes sidewalls defining an open end (26) and a curtain track (27) proximate the open end. The curtain is sized to cover the open end. The sealing adapter is fittable to the curtain track. An entire periphery of the curtain and an entirety of the seal element are sequentially fittable to the sealing adapter.