HIPA (Pack of 2) Air Filter Cleaner for STIHL 029 039 MS290 MS310 MS390 Chainsaw Fiment models: STIHL 029 039 MS290 MS310 MS390 Chainsaw Replaces # 1127 120 1621 The air filter has a hole on the backside, make sure it's identical with your original Package include 2pcs air filter