Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 57A4243-16 found under Ultrasonic Test Block Set by Olympus Ndt Ne Inc. The National Stock Number assigned to this part is 6635009665245, 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 57A4243-16.