The component $U3$ in your project is listed with the part number MFR50SFTE52-22K1, which is a resistor. It's a through-hole metal film resistor with a resistance value of 22.1 kOhms. Resistors like this are generally used to limit the current flow, reduce voltage levels, or divide voltages within an electronic circuit.

In the context of your schematic, its function will depend on how it's connected to other components. If you provide more information on its connections, I can give a more detailed analysis of its specific role in your circuit. Does this answer your question, or is there more you'd like to explore regarding $U3$?