The KST double-ball rubber flexible joint, also known as a flexible double-ball rubber joint or double-ball rubber flexible connection, is available in various materials, including natural rubber (NR), chloroprene rubber (CR), butyl rubber (IIR), nitrile rubber (NBR), fluororubber (FKM), and ethylene propylene diene monomer (EPDM). The inner and outer linings can also be made from these rubber materials, with polytetrafluoroethylene (PTFE) also available in some options. The main frame is made of nylon cord, and the booster ring is made of multi-strand copper-plated steel wire.

Flanges can be made of cast or forged carbon steel (Q235), stainless steel (304, 316, 321), or plastics (CPVC, PPH, UPVC, and RPP).

Flange standards include national, American, British, German, and Japanese standards.

Flexible rubber joints are highly elastic, airtight, and media- and weather-resistant pipe joints.

The double-ball design increases the length and compensation capacity of the rubber joint, offering greater compensation than a single-ball design. This design compensates for axial, lateral, and angular displacement of the pipeline, ensuring stable operation and extending its service life. It also offers excellent vibration and noise reduction, significantly optimizing the pipeline's operating environment.

After the rubber flexible joint is subjected to pressure for the first time (such as installation pressure test, etc.) or before it is put into use again after a long period of disuse, the bolts should be re-pressurized and tightened before being put into operation;

for high-rise water supply or suspended water supply, the pipeline should be fixed on the hanger or bracket, and the joint should not be allowed to bear the weight and axial force of the pipeline itself, otherwise the joint should be equipped with an anti-pull-off device (its bearing capacity must be greater than the axial force of the pipeline);

when installing the rubber joint, the screw of the bolt should extend to the outside of the joint, and the bolts on each flange end face should be repeatedly and evenly tightened by diagonal pressure to prevent deviation.