If you are a scuba diver, you will need to consider buying a regulator at some point. The regulator is probably the most important piece of the scuba diver's equipment because the regulator is what allows you to breathe underwater. In this article we will review one of the most popular regulator sets: The Hollis 500SE + DC7. We will review its specs, design, and compare it to some of its competitors to see if it's the right choice for your needs.

When selecting a regulator you need to consider what your needs are; Do you occasionally dive in shallow and warm water, or do you dive more frequently and in more harsh conditions? Also, price is a factor when selecting a regulator, as many high quality regs exist on the market now that are also great values. We will compare a couple to the Hollis.

What Is the Hollis 500SE + DC7?

The Hollis 500SE + DC7 is a balanced regulator set manufactured by Hollis in the USA. The first stage is an over-balanced diaphragm design which feature four low pressure ports and two high pressure ports. The first stage is environmentally sealed, which enhances cold water protection and protects internal components from corrosion. 


Also, a diaphragm design first stage is better suited for cold water dives as breathing characteristics won't be effected quite as much and internal components are more resistant to freezing in cold water temperatures.

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The first stage is constructed of marine grade black anodized brass for enhanced durability. The second stage of the Hollis 500SE + DC7 is a pneumatically balanced servo value design which ensure natural breathing regardless of tank pressure or depth. The purge button is large and easy to operate and clears the regulator especially well.

This regulator also does not need a venturi adjustment switch to stop fee-flows during descent. Also, the Hollis 500SE + DC7 a has a side exhaust configuration that routes air bubbles away from the divers face. Breathing is very natural and responsive with this regulator. This regulator comes with a 30 inch braided Maxflex hose that is more durable and flexible than standard hoses. Overall, the Hollis 500SE + DC7 is an outstanding regulator for recreational divers, and divers that routinely dive in cold water. This regulator will give you years of worry free use.

Product Specs

The Hollis 500SE + DC7 is a balanced regulator set available in Din configuration but is adaptable to yoke. The overall weight of the regulator set is 2.2 lbs. The first stage is an over-balanced diaphragm design with 2 fixed high pressure ports and 4 fixed low pressure ports. The first stage is constructed of marine grade brass with a black anodized finish.

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The second stage of the Hollis 500SE + DC7 is a pneumatically balanced servo-valve design. The second stage is constructed of high grade plastic and chrome plated brass. The second stage feature a soft purge button for easy clearing and features a side exhaust configuration that helps keep air bubbles away from the divers face. The second stage comes with an orthodontic mouthpiece for enhanced comfort and reduced jaw fatigue. The Hollis 500S​​E + DC7 comes with a 30 inch braided hose.

This regulator can be disassembled without tools and even underwater in an emergency. This regulator is also environmentally sealed for enhanced durability, reduced maintenance, and enhanced cold water protection. This Hollis regulator is Nitrox compatible up to 40%.   

Pricing

diver in the open sea using water proof camera and he is using the Hollis 500SE + DC7 Regulator

The Hollis 500SE +DC7 is priced at approximately $600 making it a good value for such a high quality regulator. This regulator has features which is common on more expensive models making it a very good value.

How It Compares

two divers on the open sea is using the Hollis 500SE + DC7 Regulator

Image by skeeze from Pixabay

We picked a few similar products available on the market to see how they compare.     

  • Scubapro Evo Scuba Diving Regulator
  • Sherwood SR2 SRB2000
  • Mares Abyss 22 Navy

The Hollis 500SE + DC7 is a balanced regulator set manufactured by Hollis in the USA. The first stage is an over-balanced diaphragm design which feature four low pressure ports and two high pressure ports. The first stage is environmentally sealed, which enhances cold water protection and protects internal components from corrosion. 

Ease of Use

Performance

Design Quality

​PROS

  • Environmentally sealed first stage
  • Side exhaust configuration
  • No venturi adjustment needed

​CONS

  • Servo-valve second stage is a more complex design
  • Second stage components are made of plastic
  • Some users report the purge is somewhat forceful
  • warranty

Hollis offers a two-year limited warranty on this regulator.

ScubaPro MK25 EVO/A700 Scuba Regulator
  • High Performance, Reliable Scubapro Technology and Value
  • Superior Ultra-High Airflow System, Maximum Performance in All-Temperatures & Conditions
  • Internal Parts Fully Insulated to Dramatically Improve Cold Water Performance

The Scubapro MK25 700A is a rugged, stylish regulator manufactured by Scubapro. This regulator offers outstanding breathing performance and is simply one of the best looking regulators on the market. The first stage is a balanced flow through piston design which offers outstanding breathing characteristics regardless of tank pressure or depth. The first stage features two high pressure ports and five low pressure ports on a swivel turret for multiple hose routing options and freedom of movement.

The second stage is an air balanced valve design with a breathing resistance adjustment control that allows the diver to fine tune the breathing resistance of the regulator. Also, the second stage has a venturi adjustment switch which is conveniently located and easy to operate. The venturi adjustment switch allows the diver to set the regulator a to pre-dive, or dive setting which eliminates free flows that can happen when jumping off the back of a boat or swimming in the surf. The Scubapro MK25 700A is Nitrox compatible up to 40% and has a total weight of 3.9 lbs including packaging materials.

Overall, this regulator set offers outstanding performance, in a great looking design.

Ease of Use

Performance

Design Quality

​PROS

  • Fully balanced first and second stage
  • Cold water certified
  •  Outstanding breathing performance

​CONS

  • Cost
  • Venturi adjustment is necessary
  • warranty

Scubapro offers a 2-year limited warranty on this regulator.

SHERWOOD SCUBA SR2 Regulator
  • Superior breathing performance
  • One touch performance adjustment knob
  • Pneumatically balanced second stage

The Sherwood SR2 SRB2000 is a balanced regulator set manufactured by Sherwood. The SR2 is a very compact regulator set that offers outstanding performance in a compact and lightweight design. The first stage is a pneumatically balanced flow through piston design which offers outstanding breathing performance at a variety of depths and regardless of tank pressure. The first stage is also environmentally sealed to prevent corrosion of the internal components of the regulator.

The first stage features 2 high pressure ports and 5 low pressure ports on a swivel turret. The second stage is a pneumatically balanced design that offers easy and natural breathing regardless of drops in tank pressure. The purge cover is soft making it easy to clear the regulator. A breathing resistance adjustment control is built in and easy to operate, and no venturi adjustment is needed. This regulator is compatible with Nitrox up to 40%. Overall, the Sherwood regulator is an outstanding regulator set for any diver.

Ease of Use 

Performance

Design Quality

​PROS

  • Fully balanced first and second stage
  • Two high pressure ports and five low pressure ports on a swivel turret
  • No venturi adjustment necessary

​CONS

  • Not designed for cold water
  • Some divers have complained the mouthpiece is too small
  • warranty

Sherwood offers a 2-year warranty with this regulator.

Mares Abyss 22 Navy II Regulator (Black)
  • First Stage Features: CWD Kit for Extreme Temperature, High Performance in Cold Water
  • Balanced Diaphragm First Stage, Tri-Material Valve Technology, Dynamic Flow Control (DFC)
  • Chrome Plated Marine Grade Brass, Environmentally Sealed Design

The Mares Abyss 22 Navy is an outstanding regulator by Mares. This regulator is constructed of stainless steel and is lightweight due to its streamlined design. The first stage is a balanced diaphragm design that is environmentally sealed, which enhances cold water protection and longevity. The Mares Abyss 22 Navy first stage features two high pressure ports and four low pressure ports on a swivel turret for ultimate comfort and mobility. Also, Mares' Dynamic Flow Control (DFC) technology which enhances breathing performance and prevents reductions in air flow when tank pressure and depth change.

This regulator is Nitrox compatible up to 40% of O2. The second stage is a balanced downstream demand valve system which provides excellent breathing performance at extreme depths and in very cold water. The second stage has no user controls due to Mares' Vortex Assisted Design (VAD). This technology allows the regulator to keep breathing resistance to a minimum level regardless of depth and tank pressure. Also, due to the VAD technology, no venturi adjustment is necessary to prevent free flows. Mares includes its super flex hose that is more flexible and durable than standard hoses.

Overall, this is an outstanding regulator that offers industry best breathing performance and ease of use.

Ease of Use

Performance

Design Quality

​PROS

  • Fully balanced diaphragm first stage
  • Outstanding cold water performance
  • No user controls on the second stage

​CONS

  • Cost
  • warranty

Mares offers a 2-year limited warranty with this regulator.

Conclusion

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For scuba divers the regulator you choose is a very important decision. There are several factors to consider aside from cost. The needs of the diver in terms of dive conditions and use should be the most important questions that you should ask yourself before purchasing a regulator set. For example, if you routinely dive in cold water you need to consider a reg that is suited for cold water. Typically balanced diaphragm design first stages that are environmentally sealed are the best choice for cold water.

Also, you should consider the materials that are used to construct the regulator, how much it weighs, whether you take photos underwater, and whether you dive in deep water or in shallow water. For most divers, the Hollis 500SE + DC7 is an outstanding choice. This Hollis regulator is loaded with outstanding features including: A balanced diaphragm first environmentally sealed first stage, servo controlled valve that is pneumatically balanced, brass construction on the first stage, braided type hose, and comfortable mouthpiece.

The Hollis SE + DC7 is an outstanding regulator for cold water dives and features a soft purge cover that makes clearing the regulator easy. Overall, this regulator set is one of the best on the market from a company that is known for high quality regulators. 

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