Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number SIR1B20B4 found under Relay Solid State by Abb Inc. The National Stock Number assigned to this part is 5945015684514, 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 SIR1B20B4.