Depends on the series of OKO carb (and they're not very clear about which is which) The OKO 28-30 mm carbs are complete knock-off of Keihin PWK28's (the 30mm is just an oval bored barrel) They work well if you don't mind fiddling with your jetting (not necessarily any more than a keihin PWK28 but you cannot get them "prejetted" with someone's best guess as to what you need to run for jetting like you can get a new Keihin PWK28 done...
The 34 may be a PJ or PWK knockoff or it could be something OKO specific (and harder to find jets and parts for)
Do you have a link/picture?