The LCI-90i is used when the line monitoring application has a requirement to monitor all three line parameters; tension, speed and payout. See the LCI-90i spec sheet here. The LCI-80 is designed specifically for rotational applications to provide operators with only a display of speed and payout line parameters and is a rugged, all-weather replacement for panel meters. See the LCI-80 spec sheet here. Both displays utilize an electroluminescent, day-light readable screen.