Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number EL21681-1 PIECE found under O Ring by Tyco Valves And Controls Lp. The National Stock Number assigned to this part is 5331001675172, 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 EL21681-1 PIECE.