Often used in heating and cooling systems, this tubing insulates refrigerant to efficiently transfer heat between components. It's frequently referred to as refrigeration and air conditioning tubing. This tubing consists of a copper tube insulated in rubber. The copper tubing resists corrosion and has excellent heat transfer qualities. The outer insulation has a closed-cell design, so it prevents moisture from seeping through and corroding the copper tubing. This tubing is generally rigid because of the copper tubing inside and is stronger than plastic and rubber tubing. Use it in medium- to high-pressure applications.