The Kanger Subtank Ni200 Coil Heads 0.15 ohm is designed for use only with devices equiped with circuit boards capable of controlling coil temperature.It features organic Japanese cotton wicks and 0.15 ohm coils wrapped from pure Ni200 wire,allowing you to monitor and limit the temperature your coils are reaching.Because these coils are only for use on devices powered by Evolv's DNA 40 board, we have changed the color of the silicone ring on the atomizer heads from clear to Vapor Shark blue for increased safety and ease of identification.