Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number AW503-37818-4 found under Head Fluid Filter by Exstar International Corporation. The National Stock Number assigned to this part is 4330013953470, and the Federal Supply Class is 4330 Centrifugals Separators And Pressure And Vacuum Filters. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like AW503-37818-4.