Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number QQ-S-571 found under Solder Lead Tin Alloy by Federal Specifications. The National Stock Number assigned to this part is 3439000038602, and the Federal Supply Class is 3439 Miscellaneous Welding Soldering And Brazing Supplies And Accessories. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like QQ-S-571.