The economical Envoy II octopus is the same internally as the ZX 2nd stage, but does not have the adjustment knob or the heat exchanger. The Envoy II Octopus has a Venturi Control Lever that allows the diver to set the octopus 2nd stage in the Pre-Dive position until needed.
This is very important in Octopus regulators, since the Pre-Dive position is much more resistant to Venturi-Free-flows that can sometimes result in significant air-loss during a dive. The Envoy II Octopus comes with a Yellow cover and 36" hose.