Preinsulated PEXa pipes expand and contract when subjected to heating and cooling.
These fixed points allow a clip to be installed between the PEXa and the internal pipework and must be used to anchor both ends of every pipe run.  We suggest a securely fixed galvanised steel munsen ring. 
This is essential to stop the expanding and contracting damaging system pipework connected to the preinsulated.
Refer to tech spec for more guidance and installation instructions.