DDQ im not sure on the size off hand. I put the "sleeve" more or less a plug, on the inside of the stem, Its about 6 inches long for support but only left a 2 inch gap. I was going to put another sleeve on the outside but never got around to it.
These are some renthal fat bars
And sme moose racing TRX bars http://www.motorcycle-superstore.com/4/22/263/5107/ITEM/Moose-Racing-Competition-ATV-Handlebar.aspx