The invention relates to a process for preparing gel-type cation exchangers of high stability by sulfonation of crosslinked acrylic ester-containing bead polymers with sulfuric acid having a concentration of 90 to 95% in the absence of a swelling agent. First and second inner guide rollers are disposed along the tape path on opposite sides of the readwrite head and adjacent to the readwrite head. The stents are formed by subjecting one or more powdered metals in a die cavity to a pressure treatment followed by a heat treatment. The second connecting terminal member has a different length than the first connecting terminal member.