Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 65B-5A-0031 found under Calibration Set Primary Referenc by Siemens Water Technologies Corp. The National Stock Number assigned to this part is 6695002526606, 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 65B-5A-0031.