Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number AL10C28HC ITEM 21 found under O Ring by Duffnorton Co Inc. The National Stock Number assigned to this part is 5331012671719, 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 AL10C28HC ITEM 21.