I recently spoke with Nicole from customer service and she told me that a number of people call and ask about Line Set sizing.
A line set is used to connect an indoor evaporator unit to the outdoor condenser in a ductless mini-split air conditioning system. A line set includes a supply and return line, which runs cooled R410-A refrigerant between the outdoor compressor and the indoor cooling unit to push cold air into the room.
You size these units based on specs from the Indoor unit. We put together a video where Nicole explains how to do this on our site. Check it out.