Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 503909 found under Cylinder Assembly A by Big Joe Mfg Co. The National Stock Number assigned to this part is 3040012287621, and the Federal Supply Class is 3040 Miscellaneous Power Transmission Equipment. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 503909.