Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number X4B51 30 1 7 O found under Filter Assembly Ele by K And L Microwave Inc. The National Stock Number assigned to this part is 5915005038050, and the Federal Supply Class is 5915 Filters And Networks. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like X4B51 30 1 7 O.