Dive Blog

Choosing A Sms Sidemount Systems


History of Sidemount

Since the early 1960’s, cave and sump divers have been using Sidemount related equipment to conduct their dives. These divers required smaller tanks that could be configured to overcome space restrictions. They also required more tanks to provide extended lateral penetrations. Tanks were ‘slung’ around the divers to meet these requirements. These Sidemount systems were developed by the divers themselves from existing dive equipment, as no commercially made Sidemount systems were available at this time.

As of the mid 90’s, Sidemount systems were becoming increasing more popular and commercial operators/manufacturers were forced to begin producing commercial Sidemount systems to cater for this market.

In the past 20 years the dive industry has gone from a single commercial Sidemount system to almost 50.

Why dive Sidemount?

There are many reasons divers choose to dive Sidemount. These range from comfort reasons, to extended dive times, to technical diving needs. Some of the benefits are as follows:

  1. Increased Gas Supply. Two (2) independent air sources for redundancy and/or extended dive times. Recreationally, you get to dive twice as long as single tank divers, so you can see areas single tank divers don’t, and experience twice as much!
  2. In Sidemount, you have an increased ability to move weight and the cylinders for proper trim, creating a more natural and comfortable position in the water. This reduces fatigue, stress, and improves air consumption!
  3. Sidemount is great for a variety of recreational diving activities. Even if using a singular tank in Sidemount configuration. It is suitable for a number of entry’s & exit’s –both on shore and from a boat.
  4. Improved streamlining – when either single or dual cylinders are required, Sidemount can reduce drag and avoid contact with overhead environments.
  5. Easier Equipment Transport. With Sidemount you have the ability to transport 2 smaller independent tanks to the water before gearing up, reducing weight on land and during entry/exits.
  6. You have an increased ability to access gear (valves/hoses etc) underwater should you have any equipment issues.
  7. Problem Solving/Redundancy. With a two (2) cylinder Sidemount configuration you have two (2) independent regulator systems, so you can handle a low on air/out of gas problem without needing your buddy’s primary alternate air source.

Okay, so I want to become a Sidemount diver…..

Which system do I choose??

Of the 50 odd systems available, there are 3 produced by Hollis. Hollis has one of the world’s leading ranges of technical specialist diving equipment and is named after Diving Hall of Fame member Bob Hollis. They manufacture dependable and innovative technical diving equipment for your personal exploration needs. They bring engineering experience to the industry, designing the highest quality diving equipment available. Built to accommodate the beginning sport diver to the exploratory technical diver, using the most cutting edge materials and proven technologies for any condition.

Designed and Built with Pride in the USA. Whichever system you choose, the Hollis SMS range has you covered.

SMS 100



The SMS100 Sidemount system is the SMS flagship, and was designed not just with Sidemount cave divers in mind, but any diver. Whether you are a beginner, advanced, or technical diver, this system is suitable for Sidemounting twin or single cylinders, but also for use with back mounted twin tanks, rebreathers or back mounted single tanks. This system can be used anywhere from open water to the overhead environment. It has a 360 degree wing with 52lbs lift (and a dual bladder option – required for technical diving) and is streamlined for reduced drag and passing through confined spaces. It also features a 1000 denier cordura w/PU lamination outer shell and 15mm urethane internal bladder, centrally and uppermost located elbow to avoid overhead interference, and both upper / lower cam band slots for rear mounted single tanks.



The SMS75 is an evolution from years of Sidemount development, which started with the SMS100. A product that has been copied, modified and personalised. This has been the benchmark for technical Sidemount for years. While it will cater more to hardcore cave divers, the SMS75 was created to handle all environments. Proper trim is key and the wing is designed to promote horizontal diving with increased lift towards the hips where it’s needed most, and without modification. The SMS75 will also support rear mounted tanks and reversible inflator positions.



Built for Sidemount only, the SMS50 can be used in any environment from open water to overhead. It includes an adjustable, one size fits most harness based on a minimalist design; also ideal for traveling Sidemounters. Ready to dive out of the box (RTD). Recommended for use with aluminium tanks and a drysuit on deeper dives due to its’ smaller lift capacity. The SMS50 features an inner located elbow to avoid overhead interference, built-in trim pockets, 23 lbs lift, and the rugged 1000 denier cordura.

Decision Time……

So, at the end of the day, deciding which Sidemount system to go with depends on what you want to do diving wise.

Here in Sydney, the SMS100 is definitely the weapon of choice. The SMS100 allows us to use single tanks (either backmounted or Sidemounted) on shore dives, twin tanks or dual Sidemount (for longer dives and the deeper technical dives), and has the additional lift and redundancy of a dual bladder for diving with steel tanks when diving at depth to explore the myriad of technically challenging wrecks that lie in the Sydney surrounds. And with the additional weight plate system that can be added to the SMS100, proper trim is easily acquired for more horizontal diving.

The SMS100 really is the one stop shop of the Hollis SMS line.