Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 153F-1 4IN ITEM 19 found under O Ring by William E Williams Valve Corp. The National Stock Number assigned to this part is 5331012862489, 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 153F-1 4IN ITEM 19.