Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 500HDF-MS found under Dehydrator Unit Nonreactivating by Zeks Air Drier Corp. The National Stock Number assigned to this part is 4440013810234, and the Federal Supply Class is . Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 500HDF-MS.