Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number ST21D30-2 found under Washer Spring Tensi by Associated Spring Barnes Group Inc. The National Stock Number assigned to this part is 5310012242564, and the Federal Supply Class is 5310 Nuts And Washers. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like ST21D30-2.