1.1 ,This specification covers the chemical, mechanical, and dimensional requirements for hardened steel Backup and Reaction washers for use with fasteners having nominal diameters of ¹/₂ ,in. through 3 in. and M14 through M80. These washers are intended for general-purpose mechanical and structural use with bolts, nuts, studs, DTIs, and other internally and externally threaded fasteners. These washers are suitable for use with fasteners covered in Specifications A354, A193/A193M, A194/A194M, A320/A320M, F959/F959M, A449, A563, A563M, and F3125.