Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 417 21 found under Lever And Bolt by Bureau Of Mines Helium Operations. The National Stock Number assigned to this part is 4820009633433, and the Federal Supply Class is 4820 Valves Nonpowered. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 417 21.