SIZE - Applicable Hole Dia: 5/16"(8mm); Under Head Size(Male): M6 x 40mm(D*L); Under Head Size(Female): 8 x 12mm(D*L); Screw Head Diameter: 12.8mm; Applicable Thickness of Locked Object: 42-49mm Application - Fit for all kinds of DIY, leather crafts, clothing making, or as a fastener to connect two objects. Such as thin photo albums, leather bags, wooden board connections, etc. Installation - Make a hole between 0.5-1mm larger than the diameter of the female rod, put the screw and nut on both sides of the locked object, and select the appropriate tool to lock it. Notice - The thickness of the object which is locked, must be less than the length of the screw rod + nut rod, otherwise, it will not be able to tighten. Advantage - Precision mechanical thread, made of carbon steel material, black powder coating, high hardness.