MRCOOL DIY25-1412-O 25 Ft Pre-Charged Mini Split Line Set is a refrigerant connection assembly designed for compatible MRCOOL DIY ductless mini-split air conditioning and heat pump systems. It works by providing a sealed, pre-charged pathway for refrigerant to flow between the indoor and outdoor units, eliminating the need for field charging during installation. https://www.partshnc.com/mrcool-diy25-1412-o-25ft-pre-charged-mini-split-line-set