Stihl Genuine Large Type Oil Cap for Stihl MS290 / MS291 / MS390 / MS391 1130 350 0533
Large type oil cap. If cap looks the same size as your fuel cap this is correct, if it looks smaller then go for the small type.
FITS:
MS290 large type oil cap
MS291 large type oil cap
MS390 large type oil cap
MS391 large type oil cap