The MX066 is a small assembled device with an on-board trim pot to control the pulse width modulator output.
Keep in mind that you should determine how hot the unit gets. If it gets too hot it will fail.
In order to be able to carry high amperage for extended periods of time, you will need to provide additional cooling.
The unit will carry up to 30 amps but not for long periods of time. Use common sense when powering large loads.

This has been a very popular module for Hydrogen Fuel cells. Use this module to regulate the amount of current going into your Hydrogen fuel cell to prevent overheating.

Power Supply: 12/24VDC
Load Voltage: 12/24VDC 30A Max.
Motor Speed: Uses PWM principle for motor speed control.
Output Frequency: 100 Hz
Motor Speed Adjustable from 0  100%
PCB Dimensions: (100 x 43 x 30mm) Approx: (4 x 1 3/4 x 1 1/8")

CONNECTING AND OTHER SPECIFICATIONS
POINT + 12 V is connected to the positive pole of the power supply 12VDC
POINT + M is connected to the positive pole of DC Motor.
POINT  M is connected to the negative pole of the DC Motor.

POINT G is to be connected to the negative pole of the power supply.
VR 10K is used to adjust the speed of the DC Motor
J is used to select the power supply 12v or 24VDC for the DC Motor.

Check out these related products:
PWM DC Motor Speed Control Module
30 A Adjustable PWM Speed Control
50 AMP PWM Speed Controller