31.8 through out the whole bar would have to be straight and for the brakeless Fixie set, since all the levers and controls are either 7/8" and 15/16" not 1.25"

Note how that Italian Road bar is so much smaller where you have to fit the Brake Levers

Grab-On foam grips will also fatten up a standard diameter bar I used 2 of the set of 4 on my Mid 80's Touring Bike ..