Abstract: A flexible plastic nipple for coupling a sprinkler head to a sprinkler system pipeline. The nipple includes an elongated plastic tube having a resilient center section and a pair of end sections. The center section has a uniform set of annular undulations which provides both rigidity and flexibility to the nipple. Each end section includes a rigid portion, a flexible threaded section, and a snub portion for mating the nipple with a connector fitting on the sprinkler head or pipeline. The threaded portions have sufficient flexibility to prevent rupturing or stripping when a force is transmitted to the nipple. In addition, the center section will bend before the force transmitted to the threaded portions becomes excessive and will rebound to its original position when the excessive force is removed.