Used a shim to fill the space. I guess you are speaking of a quill stem. Peterwhitecycles sells shims for this purpose, as does Harris cyclery. I made mine out of a piece of aluminum plate I had. Cut it out with sissors and carefully tucked it into the gap and tightened it down. So far so good, i really tried to move the bars after I set them in place, no movement.DoubleTap said:As a practical matter, is it possible to fit a 25.4 mm diameter handlebar in 26.0 mm stem?