Adjustable shunt reference in a TO-92 — what you get
The ±2.2% tolerance on the reference voltage is the figure that governs your output accuracy — if your rail needs tighter than that, you pick the TL431B variant.
Field-swappable — no lab required
The TO-92-3 package is through-hole, which means you can swap this part on site with a basic soldering iron and a pair of cutters. No hot-air station, no reflow profile. The three leads are spaced on a standard 0.1-inch pitch, so it fits protoboard and legacy PCB layouts without a footprint change. Orientation is obvious: the flat face of the TO-92 body marks the front, and the pinout (cathode, anode, reference from left to right when the flat faces you) is consistent across the whole TL431 family. If you carry a few of these in your field kit, you can fix a dead reference rail in a power supply or a failed threshold comparator in a controller without bringing the board back to the bench.