question about Campy/Fulcrum road tubeless valve
 

What is the purpose of the round washer that comes with the Campy/Fulcrum M-102 road tubeless valve? (Package contents are: outer part of valve with square rubber that seals the rim, inner valve core, "wrench" tool to tighten valve, valve cap, and round washer.)

There are no instructions (or exploded diagram) in the packaging or in my Eurus wheel manual, and I've Googled to no avail. I'm assuming maybe it goes into the outer valve before the inner one is put in. ???

While I'm asking, how tight should the inner valve be? I'm assuming just over finger tight, but again ... no instructions.

Picture of valve at: http://aebike.com/page.cfm?action=de...=30&SKU=RM6091

Thanks in advance,
John