Atomic Aquatics Z3 Regulator - Second Stage OnlyCOMPACT. ECONOMICAL. HIGH PERFORMANCE. The Atomic Z Series offers a unique combination of performance, ergonomics, features and materials. All in our most cost efficient regulator system without compromising performance or durability. The Titanium Zirconium second stage is your choice of all black styling with the Z3 (with optional color kit available). Second Stage Features: Precision machined Brass with Zirconium plating and Titanium components.