Registered Forum User
GTL
Bikes: ST4s ABS
Posts: 480
Join Date: Aug 2003
Location: Tayside, Scotland
It is also the seal that keeps the fluid in and the air/moisture out. Leave it where it is if you want your clutch fluid and pistons/seals/cylinders to stay in good nick. It is collapsible and should be pressed flat into the cap when fitting after topping up the reservoir. There are similar ones in the brake reservoirs.
[Edited on 15-7-2004 by Derek]