Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 3975-28-001 found under Gear Assy Speed Dec by S S Precision Gear And Instr. The National Stock Number assigned to this part is 6680000772933, 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 3975-28-001.