Bought these thinking they were 3.0 inch silencers, that's what they were labeled as on eBay... They're not. Typical N1 fart can diameter. Just under 4 inches wide.
DC Sports Muffler Silencer 3" Diameter SIL3000: eBay Motors (item 280430280610 end time Jun-25-10 14:40:03 PDT)
^link to the actual ones I bought... see why I thought they were 3 inch silencers?

turns out they're
FOR 3 inch DC sports muffler systems. Which have 4 inch tips.
I have two. I want $20 each. PM me.