consisting of a piston base body (2)

having a piston crown (3),

having pin bosses (5, 6) disposed on the side of the piston (1) facing away from the piston crown (3),

having pin bores (7, 8) formed into the pin bosses (5, 6),

having skirt elements (9, 10) that connect the pin bosses (5, 6) with one another,

having a circumferential region (34) that proceeds from the piston crown (3), is disposed radially on the outside, points axially in the pin boss direction, having

a circumferential collar (12) that is disposed at a slight axial distance from the piston crown (3), formed onto the radial outside of the piston (1), points radially outward, is at least approximately rectangular in cross-section, which collar has a circumferential outside thread (13) radially on the outside, the diameter of which is less than the piston diameter, and furthermore having

a recess (14) that follows it on the piston crown side, and

furthermore consisting of a ring-shaped groove reinforcement (4) having a circumferential projection (20) that follows its face and points radially inward, which is followed, on the pin boss side, by an inside thread (19) by way of which the groove reinforcement (4) is screwed onto the outside thread (13), whereby a contact surface (23) of the groove reinforcement (4) that lies on the pin boss side makes contact with a contact surface (24) that delimits the region (34) on the pin boss side and thereby closes off the recess (14) to form a ring-shaped, closed cooling channel (21), and whereby the ring belt (16) of the piston (1) is disposed partly on the radial outside of the groove reinforcement (4) and partly on the radial outside of the piston (1) that follows it, on the pin boss side, wherein the collar (12) has a bend in the pin boss direction radially on the outside, and a radial width that is sufficient for an elastic resilience in the axial direction.