Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 128K1-51H found under Retainer Electron Tube by Interplex Nascal Inc. The National Stock Number assigned to this part is 5960002494973, and the Federal Supply Class is 5960 Electron Tubes And Associated Hardware. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 128K1-51H.