Piston for a disk brake, disk brake having at least one piston, and series of pistons

A piston for a disk brake, the piston comprising:

• a contact surface for a brake lining, an outer part forming a piston skirt and an inner part inserted into the outer part;
• the inner part has an opening on a side thereof facing away from the contact surface and, in an interior thereof, a receptacle via which the piston is pressurizable by at least one of a hydraulic fluid or by an actuating means of a parking brake drive;,
• a cavity formed between the outer part and the inner part the cavity is closed fluid-tight manner by at least one fluid-tight connection between the inner part and the outer part to prevent ingress of hydraulic fluid from the receptacle of the inner part into the cavity.