I had one. Didn't like it. The surface finish was relatively rough compared to other brands, and I also saw some scratches inside the one I had. To me, that indicated a very soft metal that wasn't durable. Not something I want in my guns.
GREAT price, though... if that's all you care about, then they could work, but me personally, I would rather just stick with a stock Marui barrel, which are actually manufactured very well.