Alternative Keg Lid O-rings

[pornstache]

These look interesting, I saw Bug mentioned them in an older post:
posting.php?mode=post&f=5

Does anyone know what they're made of, if McMaster carries them, etc?
Thanks!

[Whitebeard_Brewer]

Link doesn't work.....takes you to a "New post" window

[pornstache]

Doh!

http://www.williamsbrewing.com/KEG_LID_SEALING_O_RING_P58C78.cfm