I don't know. Mine is a "z-stem" brand I got for $10 off the clearance table. I was pretty happy with it until a couple weeks ago when the bars came loose during my commute for no apparent reason. I have since tightenned it up and it's doing fine again. Those bars are on my SS road bike conversion with 48x17 gearing. It is rocking moustache bars. I think that the flex in the stem combined with climbing hills in the relatively tall gear loosened the bolt. You know...flex left...flex right...equals a potential loosening action. Probably would have been fine on a geared bike with narrower handlebars.