Tweetop fittings are a brand of press fittings used in modern plumbing and heating systems, particularly with MLCP (multilayer composite pipe) and underfloor heating installations. They create secure, leak-proof connections by pressing the pipe into the fitting using a U-profile pressing tool, which compresses the joint with the help of integrated EPDM O-rings and a stainless steel clamping ring. 
How they work
Connection method: Tweetop fittings are a press-fit system, meaning they are assembled by pressing the multilayer pipe into the fitting's profile.
Pressing tool: A specific pressing tool with U-profile jaws is used to complete the connection.
Sealing: The system uses two integrated EPDM O-rings to ensure a tight, leak-proof seal.
Clamping: A stainless steel clamping ring provides added strength and reliability to the joint.
Material: The fittings are typically made from high-quality brass, often with a nickel-plated exterior for corrosion resistance. 
Applications
Water and heating systems: Tweetop fittings are designed for reliable connections in both hot and cold water installations.
Central heating: They are suitable for connecting radiators and other components in central heating systems.
Underfloor heating: The system is ideal for underfloor and wall heating installations, ensuring efficient heat distribution.
Transitions: They can also be used for transitioning between MLCP pipes and other materials, such as copper.