MRCOOL DIY25-1412 25 Ft Pre-Charged R-410A Connection Line Set is a refrigerant line assembly designed to connect indoor and outdoor units in compatible ductless mini-split HVAC systems. It works by providing a sealed pathway for refrigerant flow between components, and its pre-charged design simplifies installation by eliminating the need for field charging. https://www.partshnc.com/mrcoolr-diy-line-set-diy25-1412