Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number SS-63TMS8-ST ITEM 21 found under O Ring by Whitey Co. The National Stock Number assigned to this part is 5331011339304, 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 SS-63TMS8-ST ITEM 21.