... onSizeM6-M42 LengthM16-300Type of headSquare,Hex,Flange,Hex socket,T-Head and other you can chooseSurface treatmentBlack Oxide,Zinc ... your sampleRegarding to Nuts Type of NutSquare,Hex,Flange,Hex socket,T-type,Coupling,wheel ,acorn,tapper,and so onRegarding to ... Washers Type of WasherRound ,Square,Plat,Friction,Plate ASTM A325 NUTS AND BOLTS HARDWARE