my friend has one and it works pretty well, im not sure if its the same manufacturer as the one you saw, but it does its job. keep in mind that it makes a loud sound while winding and it will make your magazine larger and heavier, so it may not fit in the m4 mag pouches with the winder on it. but if youre going to spray so much you will need an auto-winder, just get a box mag :lol:
