A method for manufacturing a metal mask that facilitates easy dimensional control in the manufacturing process and can manufacture multiple metal masks having high and consistent precision. The replacement part includes a storage unit that stores therein information including identification information unique to the replacement part. The telescopic arm consists of two parts, which are interconnected with a pivoting mechanism. Thereby, the semiconductor memory device enables stable refresh operation to be executed. A method for preparing the material, a method for separating from a liquid substances that selective bind to saccharides, and a device including the separation material are also disclosed. The acrylic impact modifier imparting excellent impact resistance was invented by employing multi-stage polymerization and at the same time by controlling the swelling index of rubber particles by changing the degree of cross-linking from stage to stage.