A cased A-coil is an evaporator coil housed in a metal cabinet, typically used with a furnace or air handler. The MRCOOL 4.5 Ton Pre-Charged Cased A-Coil is a powerful example for larger residential setups. These are often used when upgrading traditional split systems to more efficient refrigerants. You can find various sizes in our Accessories category. The casing protects the delicate fins of the coil from damage during installation. It is designed for high-performance heat transfer in central air applications.