An M-coil is a type of evaporator coil shaped like the letter 'M' to increase the surface area for heat exchange. The MRCOOL 4.5 Ton Pre-Charged M-Coil is a high-efficiency alternative to standard A-coils. These are often used in compact air handlers where space is limited. You can find these specialized coils in our Accessories section. The M-shape allows for a shorter cabinet while maintaining high cooling capacity. It is a great choice for modern high-SEER central air upgrades.