Genuine Aprilia washer for saddle bolts and KTpins.For '98-'03 Mille, Mille-R, '02-'05 Tuono, '04-'07 RSVR, RSVR Factory, and '06-'07 Tuono.
This is the 'top-hat' shaped washer that is inserted into the seat mounting tabs.
This part is also used as a coolant overflow mount washer on '03-'05 Atlantic 500, '01-'04 Futura, and '01-'07 CapoNord.
Aprilia part no 8221145
The part location is highlighted in red in the diagrams below: