OP, you have to read the description on buyairsoft.ca's website. Seriously: they say everything there
The Nylon/Fiber composite the externals are constructed of are of the highest quality you would find on real firearms. Then the upper receiver, we had to check with our supplier to confirm that it was not metal! The upper receiver is constructed of a very hard/ cold to the touch Nylon/Fiber composite also with a very nice rough finish.
the "real" G&G is full metal (although not the highest quality) and sit at around 550-600 for a gun. So for $300, go figure.