Before testing the machine, you must first connect the wire---fix the motor---install the case---tighten the screw---make sure that the square shaft of the can be easily rotated without jamming---connect the power supply--- Press down the speed control switch so that there is no space in the shell! Otherwise, there may be a buzzing alarm! To prevent damage to the motherboard, please follow the requirements. Colour:As shown Material:Plastic + Metal type:B Package Contents: 2 x Control board Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm. Control board drive voltage: 18V (5 strings of lithium batteries, fully 21V), power 300W. Brushless sensorless angle grinder drive control board general The product is suitable for 2106/161/169 brushless electric wrenches. It has been tested before selling OK. The battery pack marked with 48V, 68V, 88V, 98V, 128VF or TV can be used, and its voltage is actually 18V (5 series 2 parallel 10 cells or 5 series 3 parallel 15 lithium batteries, fully 21V) . 18V 21V Brushless Angle Grinder Drive Plate Polishing Machine General Control Panel Size 5.2x6.2CM