The Star Z-70B was an incremental improvement on the earlier Z-62 and Z-63 submachine guns adopted by the Spanish military and security services. It remains an open bolt, selective fire design, with an underfolding stock. The trigger has changed from a progressive type to a standard trigger with a 3-position safety/selector lever (safe, semi, full). In addition, the Z-70B was chambered for 9x19mm instead of the more antiquated 9x23mm Largo cartridge.

While the stock geometry lends itself to the gun climbing in fully automatic, I was pleasantly surprised by how nice it was to shoot. Not the world's best 9mm SMG, but far from the worst! These are still in service with Spanish armed forces in some roles, and one can certainly understand why.