Unique Internal Flex Joint Reinke’s patented and exclusive, sometimes copied, Internal Flex joint encompasses only a 4 foot section of the water carrying pipe apart from the span pipe. This unique and versatile design allows Reinke water pipe to be interchangeable since the tower is attached to the joint and not the span pipe. The internal flex joint is a critical part of the flexibility and strength of a Reinke system. Three-axis flexibility with center-line rotation reduces structural stress and extends the boot life. Reinke’s innovative parallel linkage and alignment controls centered over the hinge point of every span, provides for a more precise alignment over varying terrain.