Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 1661-121-753 found under Tap Set Thread Cutting by Time Fastener Co Inc. The National Stock Number assigned to this part is 5136014417891, and the Federal Supply Class is 5136 Taps Dies And Collets Hand And Machine. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 1661-121-753.