My cartridge does not seem to have that bolt, are there more than one style of cartridge?

Also, why would I have a coworker - takes two, to do an oil change
(One woman, bent over, and myself.. that is)

Hi, I cannot for the life of me figure out what the small O-ring is for in the oil filter (cartridge style) I purchased. The large o-ring is obvious. Attached picture of small o-ring 2009-vibe-cartridge-oil-oring.jpg (Also what is the plastic piece for? Throw it in the garbage?) My guesses: the plas...