Cressi AC2/XS2 Scuba Diving Regulator

Cressi AC2/XS2 Regulator: Entry-Level Piston Regulator for New Divers

The Cressi AC2/XS2 is a complete first and second stage regulator set, built around a straightforward piston design that prioritizes reliability over complexity.

If you are newly certified and shopping for your first personal regulator, this is the kind of gear worth considering. It is also a practical choice if you need a dedicated regulator for a stage bottle (a secondary tank clipped to your rig to extend your air supply or carry a different gas mix).

How the First Stage Works

The first stage is the part that connects to your tank valve and drops the high tank pressure down to an intermediate pressure your second stage can use.

The AC2 uses a non-balanced flow-by piston design. "Non-balanced" means the effort required to breathe can increase slightly as your tank pressure drops over the course of a dive. At recreational depths and with a reasonably full tank, most divers will not notice this in any meaningful way. It is a real distinction, but it matters most at depth or with a near-empty tank, which is not where new recreational divers typically spend their time.

The first stage body is chromed brass, a material that handles saltwater well and holds up over years of use when rinsed and maintained properly. It is manufactured in Italy, and the whole set carries EN250/2000 certification, the European standard that verifies a regulator performs safely across its rated conditions.

Port count matters when you are planning your hose setup. The AC2 gives you:

• 4 low-pressure ports (3/8" thread), for hoses to your second stage, your buoyancy compensator inflator, and any accessories like a dry suit inflator or an octopus (backup second stage)
• 1 high-pressure port (7/16" thread), for your submersible pressure gauge or dive computer transmitter

Four low-pressure ports is a comfortable number for a recreational setup. You are unlikely to run out of ports.

A conical filter sits at the tank connection. The larger surface area of a conical shape, compared to a flat disc filter, allows air to flow more freely into the first stage. It is a small design detail, but it contributes to smoother overall airflow.

The Second Stage

The XS2 second stage is the part you breathe from directly. Its housing is made from high-tech polymer plastic, which keeps weight down and resists corrosion. The mouthpiece is silicone, which is comfortable for extended use and easy to replace if it wears out.

The mechanism inside is a downstream demand valve. "Downstream" refers to how the valve fails: if something goes wrong, the valve opens rather than closes, meaning air flows freely to you rather than cutting off. This is the standard and safest configuration for recreational regulators.

Two adjustments are worth knowing about:

• Venturi adjustment: A lever or switch that controls airflow characteristics inside the second stage. Set it to "dive" once you are underwater and breathing normally. Set it to "pre-dive" at the surface to prevent the regulator from free-flowing (releasing air continuously) before you descend.
• Dive/pre-dive function: This is the same control. Switching it before you enter the water is a simple habit that protects against wasted air and an unexpected rush of bubbles at the surface.

Air is channeled to the mouthpiece in a way that creates a Venturi effect inside the second stage. This uses the momentum of the incoming airflow to assist delivery, which reduces the effort needed to draw each breath.

Weight and What's Included

The complete set with hose weighs 35 oz (994 g). That is a solid, mid-weight regulator, not ultralight, but not heavy for what it is.

The package includes the first stage, the XS2 second stage, the connecting hose, and an owner's manual.

Who This Regulator Is Not For

The AC2/XS2 is not the right tool for cold water diving. The non-balanced piston design and the overall build are suited to temperate and warm recreational conditions, not frigid water where ice-resistant (cold-water rated) internals become important.

If you are an advanced diver planning deep dives, extended bottom times, or technical profiles, you will want a balanced first stage that maintains consistent breathing effort regardless of tank pressure or depth. The AC2 is not that regulator.

It is also worth noting that this set comes with one second stage. Most divers add a separate octopus (alternate air source) for redundancy. You have enough low-pressure ports to do that, but the octopus is a separate purchase.

The Bottom Line

The Cressi AC2/XS2 does what a first regulator needs to do: it delivers air reliably, it is built from materials that last, it carries a recognized safety certification, and it is straightforward to use and maintain.

For a new diver building their first kit, or for anyone needing a dependable stage bottle regulator, it is a practical, honest choice without unnecessary complexity.