Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 4P2521 found under Rotor Engine Poppet Valve by Caterpillar Inc. The National Stock Number assigned to this part is 2815013232111, and the Federal Supply Class is 2815 Diesel Engines And Components. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 4P2521.