STIHL Genuine 044, 440, 046, 460, Rubber Air Baffle. # 1128 141 6300

Rubber air baffle or vent that fits onto the top of the aircleaner base plate, it's item no 13 in the last image from the parts list.
This part is often missing from older saws so if you're needing one here it is...Quality manufacture as you expect from STIHL