Is that the anatomy of a Sportster muffler, or the anatomy of half of a Sportster muffler?

That's interesting.  I have 2 sportster muffler's that I won on Ebay a few weeks back.  I'm going to mount one on mine to a little better sound.  I also noticed that the ones I have (from a 1200) both are completely blocked with the baffle?  Is that normal?  I went ahead and drilled a 1/2" hole in the middle to hopefully get a better flow and sound through it.  

-Matt

IS that white insulation stuff ( kinda looks like fiber glass material, first pic item at bottom ) important??

Reason i ask is that i have a supertrap on mine, it was making a rattle that drove me nuts! i decided to investigate so i took out the baffle and that insulation stuff was like barley there...

Some of the material got so hot (im assuming here) small peices hardened and were rattling around in there like a bunch of small rocks. i took what little bit that was left out (about half of it) i didnt think it would be doing its job or it would at least half assed one lol.

should i replace that? what does that stuff do anyway?

I've seen my share up muffler packing and I was quite impressed with the sportster's setup.  That is probably the most dense packing I've seen in a muffler.  It's wrapped on itself almost 3 times around so only a small section of it is actually exposed.  Plus, I can see by the quality of the fiberglass used and by the design of the retainer tube that a bike will wear out before this packing does.