OK, I thought you meant the outside diameter.
I'm sure my Renthal bars on the Monster are fairly thick-walled, certainly thicker than the clip-ons on my other bikes and so needed smaller ID bar-ends.
The picture on that ebay listing appears to show 2 different internal fitments for the bar-ends so may work OK with the smaller ID? Unless you fit them directly to the bars which is what I'd recommend if you can get away with it.
Be interested to see the mirrors though because they are certainly a better price than the CRG.