Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 1021-3172 found under Adapter Fluid Filter by Hatch And Kirk Inc. The National Stock Number assigned to this part is 4330003508927, 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 1021-3172.