We claim the ornamental design for an air filter element, as shown and described.
FIG. 1 is a front elevation view of the air filter showing our new, the rear elevation view is identical;
FIG. 2 is an enlarged view of the circled region “FIG. 2” of FIG. 1;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is an enlarged view of the circled region “FIG. 4” of FIG. 3;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is an enlarged view of the circled region “FIG. 6” of FIG. 5;
FIG. 7 is a bottom rear perspective view thereof; and,
FIG. 8 is an enlarged view of the circled region “FIG. 8” of FIG. 7.
The broken line showing of the air filter element is included for the purpose of illustrating portions of the “article” and forms no part of the claimed design.