Features:

The DC Motor Speed Controller allows controlling speed of a DC motor using a Pulse-Width-Modulated (PWM) DC voltage with a Duty Cycle fully adjustable from 10%-100%.
The motor speed controller can provide a continuous current of 8A to your DC motor or other DC load.
The circuit also includes a 10A fuse, with reverse connection of power supply and control voltage over-voltage protection function.
Specification:

100% brand new
Input supply voltage: DC 12V-40V
Maximum output power: 400W
Maximum continuous output current: 8A
The overload and short circuit protecting current is 10A
Static Current: 0.02 A (Standby)
PWM frequency: 13kHz
Duty Cycle adjustable: 10%-100%
Operation environment temperature: -20℃-40℃
Dimension: 6cm x 5.5cm x 2.8cm/2.36"x 2.16"x1.10"(approx)
Package included:

1 x DC Motor Speed Controller
Note:

This can NOT be used to the BRUSHLESS motor.
The DC motor speed controller can NOT be connected directly to AC power (eg: home 110V AC), otherwise it will burn.
Do not reverse the positive and negative DC power supply, otherwise it will damage the controller. Double check all connections before applying power and always turn off the power supply before making any wiring changes.