These high quality acetal fittings are made with EPDM o-rings that are reliable, will not perish like cheaper rubber. The acetal plastic is also chemical and UV resistant so it will last for a long time even in testing conditions.

This product is ideally suited to the 6.5mm (1/4") PE Tubing that we sell here.

This fitting is a push in fitting so you just push the line in from both sides.  It's similar to John Guest or Sharkbite.  Just cut the line of square, ensuring a clean cut surface then push into the fitting to make a reliable seal.