This may be well known to many of you, but to me as a newbie, it was a surprise. Magpul makes two levels of its acessories. One is called MOE (Manufacturers Original Eqpt?) and one is PTS (Professional Training Simulation). These parts can be named exactly the same and fit exactly the same. For instance, I was looking for a replacement fore end for my Sport. The PTS (as are all PTS items) is plastic and made for air rifles. In the case of this fore end, the PTS model does not have a heat shield. Even the small rail pieces are plastic if listed as PTS. All MOE models/pieces are metal. On e-bay, it is not always clear which you are getting and the PTS models are generally cheaper. Hope this saves one person some grief.