ok this is what i did took the impellar off the rio 2100 and the xp4 compared the two theyre both the same size or the rio is slightly larger on the magnet besides the only difference i noticed was that the rio had more impellar than the xp4 impellar did. just gotta make sure when you place it in there it fits in there snugged. trust me it works and the flow is 10 times better not that little dripping action thing, this thing flows just as good as my fx5 does. only down side of this that its a little loud
