Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number A12B21 found under Filter Cap by United Air Filter Company. The National Stock Number assigned to this part is 2945004071135, and the Federal Supply Class is 2945 Engine Air And Oil Filters Cleaners Aircraft Prime Moving. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like A12B21.