Features: Made of high quality material, durable. Input is connected to AC 220V, output is connected to electric furnace line or electrical appliances, and then turn the knob to control the speed, voltage, temperature. Specification: 100% brand new with high quality Dimensions: length 85* width 55* height 38MM, knob inner hole 6MM Maximum power :4000W(resistive load limit power), long time should reduce the power use. Efficiency: over 90% Working voltage: AC 220V Regulating voltage: AC 10-220V Fuse: 5*20 20A Some applications: Precautions for electric stoves, water heaters, lamps, small motors, electric irons, etc.: The load should not exceed the maximum power, otherwise it will burn the module and electrical appliances; Try to use resistive loads; greatly reduce the power of inductive and capacitive loads. (It is better to keep more than half) Package Included: 1 x Motor speed controller module Note: Thyristors are mainly used for resistive loads (linear incandescent lamps, etc.). Most single-phase AC motors are acceptable, but not guaranteed. Other types of loads shall be confirmed by buyer. A fuse is not everything. It has a response time. If the current is too high, it may burn the module in addition to the fuse. This module is AC voltage 220V input and AC output. It can only step down and adjust the voltage when it is connected to a load. It is useless to connect a multimeter with no load. It is not a transformer and cannot be connected to a DC load. The colors may be a little difference for the different monitor display. Please check as much as possible to make sure the item is the one that you need. Please allow 0.5-1 inch difference due to manual measurement.(1inch=2.54cm)