Heat Sink, TO220 Package, PI48, 40mm

A TO220-packaged regulator or transistor running anywhere near its rated current builds up heat fast, and without somewhere for that heat to go, it will throttle its own output or shut down well before the circuit around it is actually finished with it. This finned aluminium heat sink clips directly onto a TO220 part and gives that heat a much larger surface area to radiate from, letting the regulator or transistor keep delivering its rated output instead of backing off under load.