First degree:

Automatic Closure Device (ACD) - prevents corrosive water from entering the first stage by automatically closing when the Legend is removed from the cylinder valve.
The unique over-balanced diaphragm design results in superior depth performance.
2 HP ports and 4 MP ports are angled for optimal hose guidance.
An eco-friendly dry system keeps water out of the main spring chamber, preventing ice buildup and protecting against sludge and contamination.

Second degree:

Master Breathing System (MBS) - MBS is a new, simple and effective way to regulate breathing efficiency. It controls the direction of the air, which changes the Venturi effect, as well as changing the opening effort. One control - two functions, it doesn't get any easier.
The pneumatically balanced second stage results in smooth and easy breathing.
The Comfobite™ bite virtually eliminates jaw fatigue.