The terminology is vast, the combinations are endless - here I will go through the basics, then give some examples of the different combinations from Scubapro.

Balanced/Unbalanced/Overbalanced Diving Regulators

These diving terms can be confusing until you know what they mean - unbalanced diving regulators perform worse as the scuba diving tank empties, and should be avoided in all but the most basic diving.

A balanced diving regulator will deliver the same amount of air at all pressures and depths - balanced diving regulators are usually mid-range and are most common.

An overbalanced diving regulator is one which makes breathing easier as you go deeper - these are usually towards the top of the range.

Yoke/A-Clamp vs DIN

These are the two different types of fitting for attaching your scuba diving regulator to your tank. Your decision will probably be based on where you are diving - in the UK the A-Clamp fitting is most popular, whereas abroad the DIN fitting is more prevalant.

Technically speaking, the DIN fitting is better as you will need this if you want to use a 300bar tank - A-Clamp is only good for 232bar, although this is by far the most common.

If you buy an A-Clamp you can buy a DIN kit (around £25-35) to convert it though, and there are also A-Clamp adapters for DIN regs for a similar price.

Coldwater safe diving regulators

When diving in the UK, especially at inland dive sites you need a regulator that can still perform. The problem is that when the air goes from high pressure in your dive tank to low pressure you need to breathe, it cools a lot - sometimes leading to freeflow when in very cold water.

There are two main ways the diving regulator companies have come up with - one is to seal the first stage completely, which some manufacturers do (Apeks for example) while others have more sophisticated systems - Scubapro's TIS (Thermal Insulating System) for example is particularly good. If you are diving in cold waters (around 5 degree celcius or lower) then you really need to choose a good cold water regulator.

Piston vs Diaphragm Diving Regulators

A piston based regulator is very simple, and provide better performance at depth. Piston diving regulators cannot be overbalanced. Diaphragm diving regulators are more complex, but are less likely to have mechanical problems as the internal parts aren't exposed to the water, which can be the case with piston based regulators.

When buying a new diving regulator, don't worry about it - both provide perfectly fine performance for almost all recreational scuba diving.

Nitrox Ready Regulators

Most scuba diving regulators are suitable for up to 40% nitrox without any modification. If you require a higher o2 content then you need to go for a nitrox diving regulator - these are usually green to distinguish them and have been properly cleaned. One other consideration is that you can't use Nitrox with titanium diving regulators.

Real World Examples - Scubapro First Stages

Scubapro MK25 - A great first stage, this is a piston based, overbalanced scuba diving regulator with Scubapro's patented TIS system making it suitable for cold water.

Scubapro MK11 - A good mid-range reg, this one is an overbalanced diaphragm model, also with the TIS for cold water diving.

Scubapro MK2 - A very simple first stage, it is piston based and very compact. It comes with the TIS for cold water diving, but is unbalanced so only really suitable for first time or very occasional divers as a primary regulator. This is a very popular first stage for pony bottles because it is cheap, and you don't need a balanced reg for a pony bottle.

Real World Examples - Scubapro Second Stages

Scubapro X650 - Top of the range, this Scubapro second stage gives you a dive/pre-dive switch, a VIVA control system to set air flow levels, some small tweaks to make it easier to breathe - and it looks really impressive! This is generally coupled with the MK25 first stage.

Scubapro R395 - This is the workhorse of the Scubapro range, it is great paired with any first stage, and is very (very) reliable and a popular choice for scuba diving school kits. It comes with a dive/pre-dive switch to stop free flow when you hit the water - however cold it may be!