Phro Roll on Cartridge Heater Eric Clapton Biography, Songs, Bands, Albums, & Facts Britannica. Optimal coverage Thermostatically controlled This CE certified, high quality thermostatically controlled cartridge heater has a sturdy magnetic base and allows for two or more units to be docked together, ideal for the busy salon. The easy grip ergonomically designed hand held unit is designed to fit comfortably into the palm of the hand. Adjustable and thermostatically controlled and rated at 42W the unit can rapidly heat up a cartridge of sugaring gel and accurately maintain its temperature for optimal consistency and coverage. There is no better way to achieve maximum coverage and consistent, professional results than with the Phro roll on cartridge heater.