Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 21B20 found under Plate Assy Front by New Sd Inc. The National Stock Number assigned to this part is 1660006331780, and the Federal Supply Class is 1660 Aircraft Air Conditioning Heating And Pressurizing Equipment. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 21B20.