... steel 2.size:you can provide it. 3.function:anti-loose, buffering Item NamePan head electronic combination screw fastenerMaterialCarbon steel, ... partsA screw, a spring washer, a square washerFunctionAnti-loose and buffering1.Product Profile Pan head electronic combination screw ... square washer form this product. Its main function is anti-loose and give the machine buffering when the machine is ...