Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 6620 OPT RK-316 found under Phasemeter by M B Electronique. The National Stock Number assigned to this part is 6625012927587, 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 6620 OPT RK-316.