The Mitsubishi FX3U-16MT/ES-A is a compact PLC main unit with 16 I/O points: 8 digital inputs and 8 transistor-sink outputs. It runs on 100–240 VAC and draws 30 W, so it fits small control panels without heavy power supply derating.
Drop-in vs FX5 series
The FX5-8EX/ES (an 8-point input module from the iQ-F series) is not a functional substitute. FX5 units use a different backplane, mounting footprint, and power rail. For a panel designed around the FX3U, stick with the FX3U-16MT/ES-A — rewiring and re-paneling would be required for an FX5 swap.