Danny, their /4 changes the base sensor count before calibration and depending on the length of your probes, there should be no need to install this device between the probe and FLC. I have 2 4' Vision Micro Systems probes in my wings and they interface seamlessly with my EI MVP-50. Their /4 device is required in line when the probe is short as in my header tank...16". Angier Ames N4ZQ -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html