OEM Aprilia Starter Shaft O-Ring -#9150500
For '06-'10 RXV, SXV 4.5 / 5.5
New starters come with this part, but you may want to grab one of these just to have a spare.
Sold each
Found in:
2009-2010 SXV 4.5/5.5 Starter Motor
2008 SXV & RXV 4.5/5.5 Starter Motor
2006-2007 SXV & RXV 4.5/5.5 Starter Motor