Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 543-1 found under Disc Valve Intake by Bureau Of Mines Helium Operations. The National Stock Number assigned to this part is 4310009638846, and the Federal Supply Class is 4310 Compressors And Vacuum Pumps. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 543-1.