Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number R137 found under Screw Safety by O F Mossberg And Sonsincorporated. The National Stock Number assigned to this part is 5305003448940, and the Federal Supply Class is 5305 Screws. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like R137.