Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number A521 found under Fusible Alloy by Fisher Scientific Co. The National Stock Number assigned to this part is 9650002545367, and the Federal Supply Class is 9650 Nonferrous Base Metal Refinery And Intermediate Forms. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like A521.