This SCR electric voltage regulator is designed for adjusting voltage, brightness, speed, or temperature when used with compatible home and industrial appliances. It connects in series with devices like electric furnaces, water heaters, lamps, small motors, or electric ironssimply rotate the knob to adjust settings.Three types are available to match different power needs:Type 1 (2000W): Works with 220V AC input, adjustable voltage 50-220V AC, made of plastic and metal, sized 4.8cm x 5.5cm x 2.7cm.Type 2 (3800W): 220V AC input, max 3800W output, adjustable voltage 0-220V AC, plastic and metal build, sized 6cm x 3.6cm x 4.3cm, approx. 77g net weight.Type 3 (4000W): 220V AC input, adjustable voltage 10-220V AC, features a 1.6mm thick FR-4 high-temperature resistant circuit board, 1.5mm thick aluminum-stainless steel case, and dual capacitors (safety & metal film) for protection; sized with a 48cm x 35cm x 30mm radiator fin, approx. 41.8g net weight.