The design ethos behind King Arms is to produce a range of products to meet different levels of gamers so that they can meet the demands of budget buyers and veterans alike. If you start off with King Arms lower end models then you can pick pick up aftermarket accessories form them to upgrade it into an improved model one step at a time.
This part is an Aluminium lower receiver, a metal body upgrade for those who bought the plastic body version of the King Arms Thompson. It has a dark colored finish so it conforms to the look of the Thompsons classic coloring.