Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 853-80740MILG21 found under O Ring by Aqua Chem Inc. The National Stock Number assigned to this part is 5331004326765, 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 853-80740MILG21.