A fluid line of thermoplastic material includes a first end section integral with a principal part of the fluid line which is at least partially undulated. A first holding rib engages behind at least one locking projection of a connecting ring. The ring engages behind a second holding rib on a second end section of the pipe. The first end section has an essentially conical initial section located adjacent the principal part of the fluid line. The initial section has an outer diameter which increases in a direction toward the free end of the first end section. The initial section is adjacent to an intermediate section whose outer diameter decreases from the greatest diameter of the initial section to the smallest diameter of a locking groove for the engagement of a first locking projection.