Will an E-mag on/off assembly work with any of the other retrovalve/RT/RT Pro style valves? What makes the E-mag on/off any different from the regular RT/RT Pro/Retro valve on/offs? I mean, is it compatible with the other RT-type valves? Or is it something that will only work on an E-mag? Are there any performance enhancing traits with this on/off? Can we buy it seperately?