.22F (220000uF), 5.5V supercapacitor for memory backup in NEC CD-based hardware.
If your TurboGrafx CD, Turbobooster Plus, Super CDROM2, Turbo Duo, or PAC-N10 no longer hold game saves, the original memory capacitor may have failed.
These .22F caps have quadruple the capacity of original NEC .047F parts. They can replace the square-shaped Supercaps in Duo hardware as well.
5mm Lead Spacing
TurboGrafx CD: C208 (CDROM Dock, Digital PWB)
Turbo Duo: C509
PC-Engine Duo: C509
Super CDROM2: C509
Turbobooster Plus: C1