The FC56125 Rubber Coupling Flexible Connector - 1.25" x 1.25" is a type of flexible pipe coupling used for joining non-pressure drain, waste, and vent (DWV) piping systems. A widely available and prominent equivalent product is the Fernco 1056-125 or Pro-Connect FC56125. 
Key Features and Specifications
Size: 1.25 inches x 1.25 inches (nominal). It is designed to fit pipes with an outside diameter (OD) range of approximately 1.40" to 1.70" on both ends.
Material: Made of durable elastomeric polyvinyl chloride (PVC) with corrosion-resistant 300 series stainless steel clamps.
Pipe Compatibility: Designed to connect various pipe materials including plastic (PVC, ABS, CPVC, Smooth Wall HDPE), cast iron, copper, steel, or lead pipes.
Applications: Primarily used for sewer, drain, waste, and vent piping applications, and is rated for use both above and below ground. It is not for use on pressurized plumbing systems.
Pressure Rating: Maximum test pressure of 4.3 PSI (29.6 KPA).
Temperature Range: Suitable for continuous temperatures from -30°F to 140°F (-30ºC to 60ºC).
Resistance: The coupling provides a leak-proof, root-proof seal and is resistant to chemicals, UV rays, fungus growth, and sewer gases.
Installation: Easy to install with a screwdriver, nut driver, or torque wrench (requires 60 inch lbs of torque); no special tools, primer, or glue are needed.
Certifications: Conforms to industry standards such as ASTM C1173, ASTM D5926, and CSA B602, and is UPC approved.