We claim the ornamental design for an air filter element, as shown and described.
FIG. 1 is a top front perspective view of an air filter showing our new design, the top rear perspective view is identical;
FIG. 2 is a front elevation view thereof, the rear elevation view is identical;
FIG. 3 is a right side elevation view thereof, the left side elevation view is identical;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a bottom rear perspective view thereof;
FIG. 7 is an enlarged view of the circled region “FIG. 7” of FIG. 6;
FIG. 8 is an enlarged view of the circled region “FIG. 8” of FIG. 2;
FIG. 9 is an enlarged view of the circled region “FIG. 9” of FIG. 3; and,
FIG. 10 is an enlarged view of the circled region “FIG. 10” of FIG. 5.
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.