Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 879-021-003 found under Oscillator Crystal Controlled by Parker Hannifin Ltd. The National Stock Number assigned to this part is 5955014634917, and the Federal Supply Class is 5955 Oscillators And Piezoelectric Crystals. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 879-021-003.