ICS produces a full aluminum piston under their "Sure Power" series. The piston is gloss black and looks to be a direct copy of the stock Tokyo Marui design but with additional reinforcement material added to the sides of the first piston tooth. The black gloss appears to be paint and is relatively easy to remove.

The black gloss coating can be observed here, as well as the lack of a tapered "lip" at the entrance to the piston barrel.