My caliper rotor push oil back in the STI. All of the sudden mineral oil started leaking.
Do you know SKU of this part? (click for larger views)
Bicycles Stack Exchange is a question and answer site for people who build and repair bicycles, people who train cycling, or commute on bicycles. It only takes a minute to sign up.Sign up to join this community
According to the ST-7020R exploded diagram at https://dassets.shimano.com/content/dam/global/cg1SHICCycling/final/ev/ev/EV-ST-R7020-4341C.pdf
That part doesn't exist as a removable part, hence why you need to confirm your exact shifter part number.
For completeness - the dealer manual is at https://si.shimano.com/api/publish/storage/pdf/en/dm/RADBR01/DM-RADBR01-07-ENG.pdf and a browse through shows no mention of removing that plate.
I think this is the part you are looking for:
The rubber diaphragms, item 17, have the part numbers:
ST-RX600 Diagram showing these parts highlighted:
ST-R7020 Diagram showing similar part names on the R7020 unit specifically: