A piston slidably inserted in the cylinder of a gas pump, said cylinder having a cylinder head and an outlet valve located near the cylinder head. The piston comprises a cylindrical piston body and a wear-reducing sheet wound one time around the piston body. The opposing edges of the wear-reducing sheet are cut stepwise, such that at least two gaps are formed between the edges, which are set apart from each other for a predetermined distance in the circumferential direction of the piston body, and such that no gap portion is formed between the edges, which connects the two gaps and extends substantially in the circumferential direction of the piston body.
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