The MRCOOL DIY16-1412-O is a 16-foot pre-charged refrigerant line set designed for MRCOOL DIY 5th Generation mini-split systems with 9K, 12K, and 18K BTU indoor air handlers. It connects the indoor air handler to the outdoor condenser, allowing R-454B refrigerant to circulate efficiently between the components for heating and cooling. https://www.partshnc.com/mrcool-diy-5th-gen-16ft-1-4-x-1-2-line-set-r-454b-diy16-1412-o