I haven't used that exact one, but I've used something similar that I purchased back in 2001 or so. It was a simple design, a black plastic box with a yellow composite video connection on either end that you put between your DVD player and VCR.
We used it to copy our Disney/Kid's DVD's to VHS and kept the original DVD's in the case.
It worked fine, but we didn't get much use out of it because soon after I got a DVD burner on the PC with DVD shrink and made dupes of our kid's movies that way.