i think that depends on how wet or dry you want your skimmer to skim. i only have a needle wheel version, and the bubble break about a .5" below where the body angles up to the neck. if you set the break point lower you should have a drier, more concentrated skim. if it breaks in the neck it will produce a more watery skim. just play with it until you get your desired skim. hope that helps, if not its at least a bump!