Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number NAS4120-04B found under Heat Sink Electrica by National Aerospace Standards. The National Stock Number assigned to this part is 5999012053101, and the Federal Supply Class is 5999 Miscellaneous Electrical And Electronic Components. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like NAS4120-04B.