MRCOOL NV25-3834-O Central Ducted 25 ft 3/8 x 3/4 R-454B No-Vac Pre-Charged Line Set is a refrigerant line set designed to connect compatible central ducted HVAC system components. It works by providing a sealed pathway for R-454B refrigerant to circulate between the outdoor condenser and indoor air handler or evaporator coil, enabling efficient heat transfer for cooling and heating. https://www.partshnc.com/mrcool-no-vac-pre-charged-line-set-nv25-3834-o