Rifled Air Conditioning Systems introduced enhanced rifled coil technology to the bus industry. The internal rifled grooving of our coils increase the surface area as much as 50% over that of smooth copper coils for a more efficient transfer of heat. As a result of the success of this industry improvement, our competitors have also begun to offer enhanced heat exchanger coils. Let the buyer beware as there are many different types of enchanced coils being offered. Some of these coils were even designed for home cooling and not for use in buses. In order to get the best results it is important that you specify the most effective coils for the bus industry = Rifled Tube Coils.