The FXpansions adaptor wraps a VST plug-in in an extra layer of code that mediates between ProTools and the plug-in, making the plug-in appear to ProTools as if it was in the RTAS format. This wrapping takes place offline, using a configuration application, and once it is complete, FXpansion claim that the adaptor code uses next to no CPU power, so the plug-ins should be nearly as efficient as in a native VST host like Cubase. No extra background programs have to be running when you use the converted plug-ins - they just appear in ProTools alongside your existing effects. This creates a wrapped plug-in that has the same latency and performance as if it were a dedicated RTAS plug-in.