Crush ring gasket?
 

I just picked up diff kit that includes fill and drain plugs with crush ring gaskets. I noticed that the new fill and drain plugs have rubber gaskets built-in (see second photo of the plugs with green rubber gaskets). Since these have the rubber gaskets, do I still need to use the metal crush rings?

http://junger12.home.comcast.net/~junger12/300/1.jpg

http://junger12.home.comcast.net/~junger12/300/2.jpg

I don't believe so, just wet the gasket with oil before install

That's what I thought. Thanks RB.