Access covers close the service opening on an air cleaner housing, holding the element in place and keeping unfiltered air, dust and water out of the clean side of the system. A cracked or distorted cover lets dirt bypass the element entirely, so it is worth replacing rather than reusing.
Covers are specific to the housing and its latch arrangement. Search by Donaldson part number, or give us the number stamped on the housing or the old cover.