Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number WVTB-ISOLEX DN-0300 ITEM 4 found under O Ring by World Valve B V. The National Stock Number assigned to this part is 5331171104189, 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 WVTB-ISOLEX DN-0300 ITEM 4.