Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number BETA 57A found under Microphone Dynamic by Shure Bros Inc. The National Stock Number assigned to this part is 5965015494942, and the Federal Supply Class is 5965 Headsets Handsets Microphones And Speakers. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like BETA 57A.