Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 81557 found under Cylinder Actuating Linear by M B Companies Inc. The National Stock Number assigned to this part is 3040012957140, and the Federal Supply Class is 3040 Miscellaneous Power Transmission Equipment. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 81557.