Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 4521-1-250 METRIC found under Bracket Mounting by Stidd Systems Inc. The National Stock Number assigned to this part is 5340015614790, and the Federal Supply Class is 5340 Hardware Commercial. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 4521-1-250 METRIC.