Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 31-6801 found under Adapter Straight Flange To Pipe by Mks Instruments Inc. The National Stock Number assigned to this part is 4730012616587, and the Federal Supply Class is 4730 Hose Pipe Tube Lubrication And Railing Fittings. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 31-6801.