This is for one (1) quality marine grade stainless steel (AISI 316) bow shackle with hexagonal sink pin. The hex pin requires a 5mm hex key or hex wrench (Allen key or Allen wrench) to be tightened correctly. Each shackle is stamped 316 and the makers mark. The shackles are marked in the imperial specification style of 5/16" (for the shackle size). The metric equivalent is generally considered to be 8mm. Not to be used for overhead lifting.
