Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number XB2-BF521 found under Switch Special by Allied Controls Inc. The National Stock Number assigned to this part is 5945013029740, and the Federal Supply Class is 5945 Relays And Solenoids. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like XB2-BF521.