Geberit 18.5cm Flush Bend Extension with Sleeve, which is used to connect the flush pipe to a compatible Geberit concealed cistern. 
Key Details and Compatibility
Product Type: A straight flush bend extension pipe with an integrated EPDM rubber sealing sleeve (also known as a flush pipe cone set or collar).
Dimensions: The pipe has a diameter of 45mm and an actual length of 181mm (or 18.5cm). It is designed to connect to an inlet/outlet pipe of approximately 55mm diameter.
Material and Finish: The pipe itself is made of durable polypropylene (PP), and the included sleeve is premium EPDM rubber with a Granite Grey finish.
Compatibility: This extension is a genuine Geberit spare part designed for specific concealed cisterns, including the Geberit Twinline concealed cistern 12 cm (UP130, 110.800). It is often used in wall-hung toilet installations.
Replacement Part: This part replaces the older art. no. 152.004.16.1.