The NP5-SD5 is popular with the Navy Seals. Fixed stock accommodates large battery. Detachable silencer (really works). Metal parts include magazine, bolt, trigger, firing selector, front and rear sights. The Marui Full-auto Tracer is an exact replacement for the stock SD silencer and it's metal too! For tactical use, we highly recommend getting a three-point sling (metal sling attachment points already on gun).