What this controller is and what the 50 ms sampling means
The Fuji Electric PXF4ABA2-FB1A1 is a self-tuning 1/16 DIN (48 x 48 mm) compact temperature and process controller with a 50 ms sampling speed. That 50 ms cycle means it reads the input and updates the output twenty times per second — fast enough to catch thermal overshoot on a small reflow oven or a plastic-injection nozzle, where a slower 250 ms controller would let the temperature wander before the PID loop corrects.
What the 1/16 DIN form factor tells you about panel fit
The 48 x 48 mm cutout (1/16 DIN) is the standard panel-mount size for compact process controllers. It fits the same panel hole as every other 1/16 DIN controller on the market, so a swap-in replacement for an existing unit of the same class requires no panel rework — just verify the wiring pinout against the old unit's datasheet.